Inflator

ABSTRACT

The present invention provides an inflator including pressurized gas, in which a discharge amount of combustion residues is suppressed.  
     High temperature combustion residues in combustion gas of a gas generating agent  36  remain in an inflator  10  and its discharging to the outside is suppressed due to the composition of the gas generating agent  36,  a temperature difference between combustion gas and pressurized gas isolated from each other by a first rupturable plate  40,  collision of the combustion gas to a wall surface  22   a  and the like.  
     Further, a compact inflator is also provided. That is, the present invention provides an inflator inflating an air bag with pressurized gas and combustion gas generated by combustion of the gas generating agent, in which the following requirements are satisfied: (1) pressurized gas contains an inert gas but it does not substantially contain oxygen;  
     (2) in the gas generating agent, a pressure is 0.8 or less;  
     (3) a mole ratio of an amount of pressurized gas and an amount of combustion gas generated of a gas generating agent is 1 to 10;  
     (4) a ratio of a mass of pressurized gas and a mass of a gas generating agent is 1 to 10;  
     (5) a mass of a gas generating agent is 1 to 30 g; and  
     (6) a charging pressure of pressurized gas is 30,000 to 67,000 kPa.

TECHNICAL FIELD TO WHICH THE INVENTION BELONGS

[0001] The present invention relates to an inflator suitable for an airbag system for an automobile. The present invention also provides aninflator in which pieces of a broken rupturable plate or combustionresidues of a gas generating agent is prevented from flowing out of theinflator.

PRIOR ART

[0002] As an inflator used in an air bag system for an automobile, thereare a type in which an air bag is inflated by using only combustion gasof a gas generating agent and also a type in which an air bag isinflated by using combustion gas of a gas generating agent andpressurized gas. In either type of the inflators, it is required thatcombustion residues generated at the time of combustion of the gasgenerating agent, for example, powdery metal or metal oxide generateddue to components of the gas generating agent is never discharged intothe air bag. Therefore, such a trial has been made that generation ofcombustion residues is suppressed by changing composition of the gasgenerating agent or a structure of the inflator.

[0003] In addition, there is a type in which an air bag is inflated byusing only pressurized gas. However, with a development of a inflatorfor an inflating type safety system for an automobile, an inflator usingpressurized gas and a gas generating agent together is attractingattention.

[0004] Also, such a trial has been made that a filter is disposed toprevent pieces of a broken rupturable plate from flowing outside, orthat generation of combustion residues is suppressed by changingcomposition of the gas generating agent, or a structure of the inflator.

[0005] As the related prior arts, there are JP-A 9-76870, U.S. Pat. No.3,966,226 and U.S. Pat. No. 4,018,457.

[0006] An essential requirement in designing the inflator is that an airbag has to be inflated by a predetermined amount within a predeterminedtime to actuate the air bag effectively, and various proposals about thestructure has been made conventionally. For example, there is JP-A8-282427. As other related prior arts, there have been known JP-B44-10443, U.S. Pat. No. 6,189,922, and JP-A 2002-166817.

[0007] Since the inflator is produced for an automobile, the weight andsize of the inflator which influences a weight of an automobile areimportant design requirements. Accordingly, further reduction in weightof an inflator is required while maintaining its original functions.

DISCLOSURE OF THE INVENTION

[0008] An object of the present invention is to provide an inflator inwhich a gas generating agent and a structure of the inflator areimproved and combined to obtain a synergistic effect so that an amountof combustion residues discharged out of the inflator is suppressed.

[0009] The present invention (I-1) provides, as one means for solvingthe above problem, an inflator in which an air bag is inflated bycombustion gas generated by combustion of a gas generating agent and apressurized medium, comprising a means for making the combustion gasstrike against one or at least wall surfaces so that combustion residuesadhere to the one or at least two wall surfaces, and also a means formaking the combustion gas contact with the pressurized medium so thatthe combustion residues contained in combustion gas are cooled andsolidified due to a temperature difference, wherein a melting point ofthe combustion residues generated due to combustion of the gasgenerating agent is equal to or more than a discharging temperature of agas generated from the gas generating agent.

[0010] Further, the present invention (I-2) provides, as another meansfor solving the above problem, an inflator in which an air bag isinflated by an action of combustion gas generated by combustion of a gasgenerating agent and a pressurized medium, comprising a means forchanging a flowing direction of combustion gas to make combustionresidues in the combustion gas adhere to one or at least wall surfaces,and also a means for making the combustion gas contact with thepressurized medium so that the combustion residues in combustion gas arecooled and solidified due to a temperature difference, wherein themelting point of the combustion residues generated due to combustion ofthe gas generating agent is equal to or more than a dischargingtemperature of a gas generated from the gas generating agent.

[0011] The above-described inventions are provided with the means forarresting the combustion residues contained in combustion gas of the gasgenerating agent respectively, the following advantageous effects (1) to(3) can be obtained.

[0012] Advantageous Effect (1)

[0013] By associating the discharging temperature of a gas generatedfrom a gas generating agent and the melting point of a combustionresidue contained in the combustion gas, generation of a massive(slag-like) combustion residue can be promoted. The temperature of thedischarged gas of the gas generating agent can be obtained on the basisof a pressure inside the tank (an actually measured value) and agenerated gas amount obtained at the time of being burnt in the tankhaving a predetermined volume and further the specific heat of thegenerated gas, for example, according to the following formula (valuesother than T2 in the formula can be obtained by calculations or thelike). When the melting point of the residue becomes sufficiently higherthan the temperature of the discharged gas (not less than 100° C.,preferably not less than 500° C.), the combustion residue can be easilysolidified and becomes massive (slag-like), and it remains inside theinflator to be suppressed from being discharged outside of the inflator.${\frac{C_{V_{1}}M_{1}T_{1}}{a} + \frac{C_{V_{2}}M_{2}T_{2}}{b}} = \frac{\left\{ \frac{{C_{V_{1}}M_{1}} + {C_{V_{2}}M_{2}}}{M_{1} + M_{2}} \right\} \times \left( {M_{1} + M_{2}} \right) \times T_{3}}{C}$

[0014] In the formula, the meanings of symbols are as follows:

[0015] a term: calorie of initial air in a tank

[0016] b term: calorie of discharged gas (gas discharged into the tank)

[0017] c term: calorie of mixed gaseous matter in the tank afteractuation of the inflator (after mixed with initial air in the tank)

[0018] Cv1: average specific heat of air

[0019] M1: the mole number of air

[0020] T1: air (before actuation) temperature

[0021] Cv2: average specific heat of discharged gas

[0022] M2: the mole number of discharged gas

[0023] T2: discharged gas temperature

[0024] T3: gas temperature after being mixed (calculated according to anformula of state of ideal gas)

[0025] Advantageous Effect (2)

[0026] By cooling the combustion gas due to a temperature differencefrom the pressurized medium, combustion residues can be solidified. Whenthe combustion gas with a high temperature and the pressurized mediumwith a lower temperature contact with each other, the combustionresidues with a high temperature are cooled and solidified to becomesmassive (slag-like) and remains inside the inflator so that the residuesare suppressed from being discharged outside the inflator. Theadvantageous effect (2) can be further improved owing to a synergismwith the advantageous effect (1).

[0027] Advantageous Effect (3)

[0028] By making combustion gas flow strike against a wall surface,combustion residues can adhere to the wall surface. Since the combustionresidues contained in the combustion gas has a high temperature and thepressurized medium has a lower temperature, the combustion residues issolidified when the residues contact with the pressurized medium as inthe above advantageous effect (2), and further, the combustion residuesadhere to the wall surface by making the combustion residues in thecourse of solidifying strike against the wall surface and thereby, theamount of combustion residues discharged outside of the inflator can bereduced. The advantageous effect (3) can be further improved owing to asynergism with the advantageous effects (1) and (2).

[0029] In order to easily obtain the advantageous effects (1) to (3) inthe respective above inventions, a preferable inflator comprises anouter shell made of a cylindrical pressurized medium chamber housing, apressurized medium chamber charged with a pressurized medium, a gasgenerator which is connected to one end of the pressurized mediumchamber and includes an ignition means and a gas generating agentaccommodated in a gas generator housing, and a diffuser portionconnected to the other end of pressurized medium chamber, wherein afirst rupturable plate closes between the pressurized medium chamber andthe gas generator, a second rupturable plate closes between thepressurized medium chamber and the diffuser portion, and further, a cap,which has a gas ejecting hole in at least one of the side surface andend surface, covers the first rupturable plate from the pressurizedmedium chamber side.

[0030] As describe above, the first rupturable plate closes between thepressurized medium chamber and the gas generator, and thereby, even whenthe gas generating agent is burnt, a sufficient temperature differenceof the combustion gas and the pressurized medium can be obtained toexhibit a solidifying effect of the combustion residues. Accordingly,even when the inflator is kept under a high temperature (for example,inside an automobile including an air bag apparatus provided with aninflator, in the summer), a temperature of the pressurized medium ismuch lower than a discharging temperature of the gas generating agent,thereby exhibiting a solidifying effect of the combustion residues.However, in case of not having the first rupturable plate, thepressurized medium is heated by the combustion heat of the gasgenerating agent, so that the temperature difference between thepressurized medium and the discharged gas becomes small, therebyspoiling the solidifying effect of the combustion residues.

[0031] Also, since the gas generating agent exist under a normalpressure, deterioration of the gas generating agent due to pressure isreduced as compared with a case of existing under a high pressure.Further, by providing the cap having a gas ejecting hole in at least oneof a side surface and an end surface, the combustion gas easily strikesagainst a wall surface of the pressurized medium chamber housing.Incidentally, in order to enhance an arresting effect of the combustionresidue, a cap can also be provided in the second rupturable plate side.

[0032] Also, the present invention (I-4) provides, as another means forsolving the above problem, an inflator comprising an outer shell made ofa cylindrical pressurized medium chamber housing, a pressurized mediumchamber charged with a pressurized medium, a gas generator which isconnected to one end of the pressurized medium chamber and includes anignition means and a gas generating agent accommodated in a gasgenerator housing, and a diffuser portion connected to the other end ofpressurized medium chamber, wherein a first rupturable plate closesbetween the pressurized medium chamber and the gas generator, a secondrupturable plate closes between the pressurized medium chamber and thediffuser portion, a cap covers the first rupturable plate from thepressurized medium chamber side and further, at least one selected fromthe following requirements (a) to (c) is provided.

[0033] (a) an inner wall surface of the pressurized medium chamberhousing is rough;

[0034] (b) the gas ejecting hole is oriented such that combustion gasejected from the gas ejecting hole does not strike against an inner wallsurface of a pressurized medium chamber housing in the shortestdistance; and

[0035] (c) a barrier member is disposed in the vicinity of the gasejecting hole, and combustion gas ejected from the gas ejecting holemoves after it strikes against the barrier member.

[0036] Since the above-described inventions are provided with therequirements (a) to (c), the following advantageous effects (4) to (6)can be obtained in addition to the advantageous effects (2) and (3).

[0037] Advantageous Effect (4)

[0038] As described in the requirement (a), when the inner wall surfaceof the pressurized medium chamber housing is rough, the combustionresidues are easily caught and arrested by uneven part of the roughsurface, so that discharging of the combustion residues is suppressed.

[0039] In order to exhibit better the advantageous effect (4), in therequirement (a), preferably, the inner wall surface of the pressurizedmedium chamber housing forming the pressurized medium chamber isprovided with a groove(s) formed continuously or discontinuously in thecircumferential direction (preferably, its depth is not less than 0.1mm, and more preferably, not less than 0.2 mm). By forming such agroove, the housing weight can be reduced corresponding to the groove.

[0040] Advantageous Effect (5)

[0041] As described in the requirement (b), by restricting the openingdirection of the gas ejecting hole provided in the cap, the number ofcontacts of the combustion gas and the wall surface can be increased(that is, a contacting time can be elongated) so that the combustionresidues easily adhere to the wall surface, and discharging of thecombustion residues outside the inflator is suppressed.

[0042] In order to exhibit better the advantageous effect (5) in therequirement (b), the aspect in which the gas ejecting hole is providedin a side surface of the cap to be oriented towards the gas generator;the aspect in which the gas ejecting hole is provided in a side surfaceof the cap and a member for circumferentially restricting the ejectingdirection of combustion gas from the gas ejecting hole is provided; andthe aspect in which the gas ejecting hole is provided in an end surfaceof the cap and a member for circumferentially restricting the ejectingdirection of combustion gas from the gas ejecting hole is provided canbe employed.

[0043] Advantageous Effect (6)

[0044] As described in the requirement (c), combustion gas ejected fromthe gas ejecting hole strikes against the barrier member, and therefore,combustion residues first adhere to the barrier member to be arrested.And a flow of the combustion gas is disturbed by striking against thebarrier member, so that the number of times of contacts of combustiongas and the wall surface can be increased (that is, the contacting timecan be elongated), and consequently, the advantageous effect (5) is alsoobtained substantially and discharging of the combustion residuesoutside the inflator is suppressed.

[0045] In order to exhibit better the advantageous effect (6) in therequirement (c), the following aspects can be employed;

[0046] An aspect in which the barrier member is cylindrical, one endthereof is integrated with the end surface of the cap and closed, theother end is opened, and a side surface is formed to face, with a gap,the gas ejecting hole provided in a side surface of the cap, and thecombustion gas moves from the opened end after the combustion gasstrikes against an inner wall of the side surface on the cylindricalmember.

[0047] An aspect in which the barrier member is disk-shaped, integratedwith end surface of the cap and is extended from the end surface of thecap towards an inner wall surface of the pressurized medium chamberhousing, and after the combustion gas ejected from the gas ejecting holeprovided in the side surface of the cap strikes against a peripheraledge portion of the barrier member, it moves from a clearance betweenthe inner wall surface of the pressurized medium chamber housing and theperipheral edge portion of the barrier member.

[0048] An aspect in which the barrier member is disk-shaped, integratedwith the end surface of the cap and is extended from the end surface ofthe cap towards an inner wall surface of the pressurized medium chamberhousing to make a peripheral edge portion thereof abut on the inner wallsurface, a gas passing port is provided in the peripheral edge portionof the barrier member and a member for circumferentially restricting anejecting direction of gas from the gas passing port is provided, andcombustion gas ejected from the gas ejecting hole provided in the sidesurface of the cap is ejected from the gas passing port.

[0049] The inflator of the above-described invention can be providedwith the requirements (a) and (b), the requirements (a) and (c), therequirements (b) and (c), or the requirements (a), (b) and (c).

[0050] Further, in the inflator of the above-described invention, suchan aspect can be employed that the cap has a flange portion formed bybending an opening peripheral edge portion outwardly and the gasgenerator housing is fixed at the flange portion by crimping part of thegas generator housing.

[0051] Further, in the inflator of the above-described invention, suchan aspect can be employed that a pressurized medium charging hole isformed in a side surface of the pressurized medium chamber housing, andthe charging hole is closed by a pin after the pressurized medium ischarged. In the inflator of the above-described invention, such anaspect can be employed that the pin is protruding into the pressurizedmedium chamber and a protruding portion thereof has such a length thatcombustion gas flow of the gas generating agent strikes against theprotruding portion. By securing some length in the protruding portion ofthe pin in this manner, combustion gas is made to strike against the pinso that the combustion residues adhere to the pin.

[0052] Also in the above-described invention, the advantageous effect(1) can further be exhibited by using a gas generating agent in which amelting point of the combustion residue generated by combustion of thegas generating agent is not less than a discharging temperature of gasgenerated from the gas generating agent.

[0053] In the above-described invention, such an aspect can be employedthat the pressurized medium chamber housing is symmetrical in the axialand radial directions. By employing such a symmetrical shape, theorientation of the pressurized medium chamber housing does not have tobe adjusted at a time of assembling, so that an assembling work isfacilitated.

[0054] In the above-described invention, such an aspect can be employedthat the gas generator housing and the pressurized medium chamberhousing are connected by resistance-welding.

[0055] The gas generating agent used in the present invention can bedetermined in relation with composition of the pressurized medium asfollows:

[0056] The pressurized medium comprises an inert gas such as argon orhelium (nitrogen is also included in the inert gas in the presentinvention). When the pressurized medium has a composition which does notinclude oxygen substantially, the argon works to promote the thermalexpansion of the pressurized medium, and helium is preferably containedbecause the leakage of the pressurized medium can be detected easily andconsequently, distribution of imperfect products can be prevented. Also,a preferable pressurized medium does not include oxygen, but oxygen maybe included to promote combustion of the gas generating agent. In caseof including oxygen, an amount of addition thereof is preferably 10 mole% or less, more preferably 5 mole % or less. A charging pressure of thepressurized medium is preferably 10,000 to 70,000 kPa, more preferably30,000 to 60,000 kPa.

[0057] As the gas generating agent, for example, it is possible to use amaterial including fuel and oxidizing agent, or fuel, oxidizing agentand slag-forming agent, being mixed with binder if required, and formedinto a desired shape. If such a gas generating agent is used, a gasgenerated by combustion of the agent can be used for inflating anddeveloping an air bag together with the pressurized medium. Especially,when the gas generating agent including the slag-forming agent is used,slag is easily made, so that an amount of mist-like combustion residuesdischarged from the inflator can be largely reduced. However, in case ofreducing a charged amount of gas generating agent and generatedresidues, it is unnecessary to use a slag-forming agent.

[0058] A preferable fuel can be one or at least two selected from thegroup consisting of guanidine derivatives such as nitroguanidine (NQ),guanidine nitrite (GN), guanidine carbonate, amino nitroguanidine, aminoguanidine nitrite, amino guanidine carbonate, diamino guanidine nitrite,diamino guanidine carbonate, and triamino guanidine nitrite. As fuel,one or at least two selected from the group consisting of tetrazole andtetrazole derivatives can be used.

[0059] As the oxidizing agent, one or at least two selected from thegroup consisting of strontium nitrate, potassium nitrate, ammoniumnitrate, potassium perchlorate, copper oxide, ferrous oxide, a basiccopper nitrate are preferably used.

[0060] As the slag-forming agent, one or at least two selected from thegroup consisting of acid clay, talc, bentonite, diatomaceous earth,kaolin, silica, alumina, sodium silicate, silicone nitride, siliconcarbide, hydrotalsite, and a mixture thereof are preferably used.

[0061] As the bonding agent, one or at least two selected from the groupconsisting of sodium salt of carboxymethylcellulose, hydroxyethylcellulose, starch, polyvinyl alcohol, guar gum, microcrystal cellulose,polyacrylamide and calcium stearate are preferably used.

[0062] when the pressurized medium and the gas generating agent composedin the above manner are used, a mole ratio (A/B) of an amount of thepressurized medium (A moles) and an amount of the gas generated bycombustion of the gas generating agent (B moles) is adjusted topreferably 0.2 to 10, more preferably 0.4 to 4. The mole ratio A/B maybe described as a mole ratio A1/A2 in the following explanation.

[0063] By adjusting the mole ratio of an amount of the pressurizedmedium and an amount of the gas generated by combustion of the gasgenerating agent in this manner, a delay in rising of an inflatorinternal pressure can be prevented and an excessive rising of aninternal pressure of the inflator can be prevented. Thus, an internalpressure of the inflator can be controlled at a time of combustion ofthe gas generating agent, and thereby, the volume of the pressurizedmedium chamber housing is reduced (that is, the length and/or the width(diameter) of the pressurized medium chamber housing is reduced), andeven if the internal pressure rises correspondingly, an internalpressure of the inflator at a time of combustion can be prevented fromrising excessively. Incidentally, in the inflator of the presentinvention, a weight ratio (X/Y) of a weight (X) of the pressurizedmedium and a weight (Y) of the gas generating agent is preferably 0.1 to7, more preferably 0.5 to 5. The weight ratio (X/Y) may be described asa mass ratio B1/B2 in the following explanation.

[0064] The gas generating agent used in the present invention caninclude 20 to 60 mass % of nitroguanidine as the fuel and 80 to 40 mass% of the oxidizing agent, and preferably, 30 to 40 mass % ofnitroguanidine as the fuel and 70 to 60 mass % of strontium nitrate asthe oxidizing agent. Further, the bonding agent (sodiumcarboxymethylcellulose or the like) and the slag-forming agent (acidclay or the like) can further be mixed in addition to the fuel and theoxidizing agent. In this case, it is preferable that the fuel is 20 to60 mass %, the oxidizing agent is 40 to 65 mass %, the bonding agent is3 to 12 mass % (preferably 4 to 12 mass %), and the slag-forming agentis 1 to 20 mass % (preferably 3 to 7 mass %).

[0065] According to the inflator of the present invention, combustionresidues contained in the combustion gas of the gas generating agent canbe suppressed from being discharged outside the inflator.

[0066] Next, the present invention (II-1) provides, as one means forsolving the problem, an inflator in which an air bag is inflated withcombustion gas due to combustion of a gas generating agent andpressurized gas, comprising a pressurized gas chamber which has a outershell formed by a cylindrical pressurized gas chamber housing and isfilled with pressurized gas, a gas generator which is connected to thepressurized gas chamber and includes an ignition means and a gasgenerating agent accommodated in a gas generator housing, and a diffuserportion which is connected to a different portion from the pressurizedgas chamber, a first rupturable plate closing between the pressurizedgas chamber and the gas generator, and a second rupturable plate closingbetween the pressurized gas chamber and the diffuser portion, wherein

[0067] the diffuser portion is a cap having a plurality of gasdischarging holes through which gas passes, and at least one of piecesproduced by the broken first and second rupturable plates and residues(combustion residues) contained in combustion gas generated bycombustion of the gas generating agent is prevented from flowing outsidethe inflator.

[0068] In this invention, any aspect can be employed such that thediffuser portion is a cap, or that a cap is disposed inside the diffuserportion, and further, the aspect in which the diffuser portion is fixedby welding to the pressurized gas chamber housing, or the aspect inwhich the diffuser portion is integrated with the pressurized gaschamber housing can be employed.

[0069] In this invention, the diffuser portion removes either or both ofpieces of the broken first and second rupturable plates and a combustionresidue to prevent them from flowing outside the inflator or to reducean outflow amount thereof.

[0070] In an inflator of the present invention (II-2), a cap, having aplurality of gas discharging holes through which gas passes andpreventing at least one of pieces of the broken first rupturable plateand combustion residues of the gas generating agent from flowing outsidethe inflator, is disposed inside the pressurized gas chamber to coverthe first rupturable plate from the pressurized gas chamber side.

[0071] In this invention, broken pieces produced by breaking of thefirst rupturable plate and combustion residues are removed by the capdisposed inside the pressurized gas chamber, thereby preventing themfrom flowing outside the inflator or to reduce an outflow amountthereof.

[0072] In an inflator of the present invention (II-3), a cap, having aplurality of gas discharging holes through which gas passes andpreventing at least one of pieces of the broken first rupturable plateand combustion residues of the gas generating agent from flowing outsidethe inflator, is disposed inside the pressurized gas chamber to coverthe first rupturable plate from the pressurized gas chamber side.

[0073] In this invention, pieces produced by breaking of the firstrupturable plate and combustion residues are removed by the cap disposedinside the pressurized gas chamber, thereby preventing them from flowingoutside the inflator or to reduce an outflow amount thereof.

[0074] It is preferable that the cap of the above-described inventioncomprises a cylindrical member having one end opened and the other endclosed, and has a plurality of gas discharging holes in at least aperipheral surface thereof.

[0075] In the cap of the above-described invention, preferably, therelationship between a distance L between a closed end surface of thecap and a gas discharging hole nearest to the closed end surface and adiameter D of the rupturable plate satisfies the following formula:L≧D/2. In this case, the distance L is preferably 3 to 8 mm, morepreferably 4 to 8 mm, and most preferably 5 to 8 mm.

[0076] The diameters of a plurality of the gas discharging holes in thecap of the above-described invention are preferably 0.5 to 2 mm and morepreferably 0.5 to 1.2 mm, and the total opening area of a plurality ofthe ejecting holes in a screen is preferably 20 to 1000 mm² and morepreferably 100 to 500 mm².

[0077] It is preferable that the cap of the above-described invention isdisposed such that the axial direction of the cap and the axialdirection of the pressurized gas chamber housing coincide with eachother.

[0078] With the above-described cap of the invention, the followingadvantageous effects (IIa) to (IIc) can be obtained.

[0079] (IIa) When the cap is disposed such that the axial direction thecap and the axial direction of the pressurized gas chamber housingcoincide with each other, pressurized gas strikes against the closed endsurface of the cap and then changes its flow direction to flow out fromthe ejecting holes in the peripheral surface. Because the gas changesits outflow direction, foreign materials (pieces of the brokenrupturable plate or the like) easily remain in a pocket portion from theclosed end surface of the screen to the ejecting hole nearest thereto.Incidentally, by mounting the screen at the flange portion in the abovemanner, no gap is produced between the screen and an inner wall of a gasdischarging port, and foreign materials are prevented from flowing outwithout passing through the screen.

[0080] (IIb) When the inflator is actuated and the rupturable plate isbroken by an igniter, a central portion of the rupturable plate ispositioned near to the igniter and a pressure of the pressurized mediumapplied from the opposite side becomes the maximum at the centralportion, and therefore, the rupturable plate is liable to be broken fromthe central portion in any event. For this reason, the maximum length ofthe foreign material produced by breaking the rupturable plate has alength corresponding to a radius of the rupturable plate. Thereby, asdescribed above, if the relationship of L≧D/2 is satisfied, the depth(L) of the pocket portion becomes equal to or more than the length (D/2)of the foreign materials, so that the foreign materials become easier toremain in the pocket portion. That is, the above-described advantageouseffect (IIa) is further enhanced.

[0081] (IIc) Since the pressurized medium enters from the opening of thescreen to be discharged through the ejecting hole on the peripheralsurface, foreign materials contained in the pressurized medium isprevented from leaking outside the inflator, and at the same time,outflow pressure of the pressurized medium is also controlled. Further,by controlling the outflow pressure (an outflow amount per unit time) ofthe pressurized medium with the screen at a time of actuation, theoutflow pressure of the pressurized medium is prevented from beinginfluenced by broken state of the rupturable plate.

[0082] The present invention (II-10) provides an inflator according toany one of the inflators described in the above (II), including meansfor changing the flow direction of the combustion gas by the cap, makingcombustion residues contained in the combustion gas adhere to one or atleast two portions of the wall surface, further making the combustiongas contact with the pressurized gas, and cooling and solidifying thecombustion residues contained in the combustion gas due to a temperaturedifference, wherein the melting point of the combustion residuesgenerated due to combustion of the gas generating agent is equal to ormore than a discharging temperature of a gas generated from the gasgenerating agent.

[0083] In the present invention (II-10), the advantageous effects (1) to(3) of the above-described invention (I) can be obtained in addition tothe above-described operations (IIa) to (IIc).

[0084] Further, in the present invention (II-10), with the firstrupturable plate closing between the pressurized gas chamber housing andthe gas generator, a sufficient temperature difference can be obtainedbetween the combustion gas and the pressurized gas and a solidifyingaction of the combustion residues can be exhibited even when the gasgenerating agent is burnt. Accordingly, even when the inflator is leftin a high temperature (for example, inside an automobile including anair bag apparatus provided with an inflator, in the summer), thetemperature of the pressurized gas becomes remarkably lower than thedischarged gas temperature of the gas generating agent so that thesolidifying action of the combustion residue is exhibited. However,without the first rupturable plate, the pressurized gas is heated bycombustion heat of the gas generating agent, and thereby, thetemperature difference between the pressurized gas and the discharge gasbecomes small, so that the solidifying action of the combustion residueis weaken.

[0085] Also, since the gas generating agent is kept under a normalpressure, its deterioration due to pressure is smaller than that in caseof being kept under a high pressure. Further, since the cap having thegas discharging hole in at least one of the side surface and the endsurface is provided, combustion gas easily strikes against the wallsurface of the pressurized gas chamber housing. Incidentally, in orderto enhance the arresting effect of the combustion residues, a cap canalso be provided on the second rupturable plate side.

[0086] The invention (II-11) provides the inflator according to any oneof the inflators described in the above invention (II) and furtherprovided with at least one selected from the requirements (a), (b) and(c) of the above invention (I).

[0087] Since the present invention is provided with at least oneselected from the requirements (a), (b) and (c), the above advantageouseffects (4) to (6) can be obtained in addition to the advantageouseffects (2) and (3). Plural combination can be applied to therequirements (a), (b) and (c) as in the above (I).

[0088] Further, the invention (II) can take an aspect in which the caphas a flange portion and is fixed as in the invention (I).

[0089] Further, the invention (II) can take an aspect in which apressurized-medium charging hole, a pin and a protruding portion areprovided as in the invention (I).

[0090] Also in the invention (II), the advantageous effect(1) can beexhibited as in the above (I). Further, a relationship among thepressurized gas chamber housing, joining of the gas generator housingand the pressurized gas chamber housing, compositions of the gasgenerating agent and pressurized gas can be provided as in the invention(I).

[0091] The gas generating agent and the pressurized gas used in thepresent invention (II) is similar to those in the invention (I).

[0092] By adjusting the mole ratio of an amount of the pressurized gasand an amount of gas generated by combustion of the gas generating agentin the above manner, an charging amount of the pressurized gas can bereduced. Thereby, even when a volume of the pressurized gas chamberhousing is reduced (that is, a length and/or a width (diameter) of thepressurized gas chamber housing is reduced), the same pressure as thatbefore a volume is reduced can be maintained without increasing acharging pressure of the pressurized gas (=the internal pressure in thepressurized gas chamber housing). Incidentally, in the inflator of thepresent invention, the weight ratio (X/Y) of the weight (X) of thepressurized gas and the weight (Y) of the gas generating agent ispreferably 0.1 to 7, and more preferably 0.5 to 5.

[0093] According to the inflator of the present invention, pieces of thebroken reputurable plate contained in a gas and combustion residuescontained in combustion gas of the gas generating agent can be preventedfrom being discharged outside the inflator.

[0094] Further, an object of the present invention (III) is to providean inflator in which size and weight is reduced without losing functionsof the inflator, and an air bag system using the same.

[0095] If an inflator utilizing pressurized gas and combustion gas of angas generating agent is made compact, maintaining a required chargedamount of the pressurized gas (a charging amount required for inflatingan air bag), an internal pressure rises because of the reduced internalvolume. And, if the gas generating agent is burnt under a high pressurewith the rising of the internal pressure, the internal pressure furtherrises due to generation of a high temperature combustion gas to exceedpressure resistance of the inflator or to raise a burning velocity ofthe gas generating agent excessively. In result, flowing speed of thegas becomes too high to keep an inflating timing of an air bag within anoptimal time for protecting an occupant.

[0096] However, when the requirements (1) to (6) determined in theinvention (III) are provided and these requirements act in mutualrelation, even in the compact inflator with rising internal pressure,the same operation as that before it is compact can be secured withoutcausing the above problems.

[0097] The invention of the invention (III-1) provides, as one solvingmeans, an inflator in an air bag is inflated by pressurized gas andcombustion gas of a gas generating agent, provided with the followingrequirements (1) to (6).

[0098] In other words, the invention of the invention (III-1) is aninflator inflating an air bag with pressurized gas and combustion gasgenerated by combustion of the gas generating agent, and provided withthe following requirements (1) to (6);

[0099] (1) pressurized gas contains an inert gas but it does notsubstantially contain oxygen;

[0100] (2) in the gas generating agent, a pressure index obtained by thefollowing formula: rb=αP^(n) (in the formula, rb: burning velocity, α:coefficient, P: pressure, and n: pressure index) is 0.8 or less;

[0101] (3) a ratio A1/A2 of an amount (mole number) of pressurized gas(A1) and an amount (mole number) of gas generated by combustion of a gasgenerating agent (A2) is 1 to 20;

[0102] (4) a ratio B1/B2 of a mass (B1) of pressurized gas (B1) and amass (B2) of a gas generating agent is 1 to 20;

[0103] (5) a mass of a gas generating agent is 0.5 to 30 g; and

[0104] (6) a charging pressure of pressurized gas is 30,000 to 67,000kPa.

[0105] The following is the detailed description.

[0106] (1) Pressurized gas contains an inert gas but it does notsubstantially contain oxygen.

[0107] The pressurized gas comprises an inert gas such as argon orhelium (nitrogen is also included in the inert gas in the presentinvention). When the pressurized gas has a composition which does notinclude oxygen substantially, the argon works to promote the thermalexpansion of the pressurized gas, and helium is preferably included sothat the leakage of the pressurized gas can be detected easily, andthereby, distribution of imperfect products can be prevented.

[0108] That the pressurized gas does not substantially contain oxygenmeans that oxygen is not included positively in the pressurized gas.There are cases such that oxygen gas is mixed in the pressurized gas ina course of charging gas or that oxygen gas is mixed in an inert gas asimpurity and can not be completely avoided, therefore, even when oxygengas is contained in the pressurized gas for such a reason, it is alsoregarded that oxygen is not substantially contained. When oxygen isincluded in the pressurized gas, a burning velocity of a gas generatingagent in the initial combustion stage rapidly rises to raise an internalpressure of the inflator. However, such a rising of an internal pressureof the inflator is avoided if the pressurized gas does not substantiallyinclude oxygen. When oxygen gas is contained in the pressurized gas, itis preferable that a content of oxygen gas is 3 mole % or less.

[0109] (2) In the gas generating agent, a pressure index obtained by thefollowing formula: rb=αP^(n) (in the formula, rb: burning velocity, α:coefficient, P: pressure, and n: pressure index) is 0.8 or less.

[0110] In the above invention, a pressure index (n) was obtained fromtwo formula of rb1=αP1^(n) and rb2=αP² after the burning velocity rb1 ina tank of a pressure P1 (70 kg/cm²) was measured and a burning velocityrb2 was measured in a tank of a pressure P2 (100 kg/cm²).

[0111] By providing the requirement of a pressure index, rapid rising ofa burning velocity in the initial stage of the combustion of the gasgenerating agent is prevented, so that rising of an internal pressure ofthe inflator is small. For this reason, even when the thickness of theinflator (the pressurized gas chamber housing) is decreased, asufficient pressure-resistance can be maintained. Also, the gasgenerating agent is burnt stably because of the small rising (that is, alittle change in the internal pressure) of the internal pressure of theinflator (pressure inside the pressurized gas chamber housing), so thatcombustion remnants do not occur. The pressure index (n) is preferably0.1 to 0.8, and more preferably 0.1 to 0.8.

[0112] Such a requirement (2) can be provided by adjusting thecomposition of the gas generating agent.

[0113] In the requirement (2), when the pressure index exceeds 0.8, thesensitivity to a pressure of the gas generating agent becomes high, thatis, a combustion is greatly affected by change in pressure, so that anumerical range in the following requirements (3) to (7) becomes narrow,which makes it difficult to conduct an adjustment for providing therespective requirements.

[0114] (3) A ratio A1/A2 of an amount (mole number) of pressurized gas(A1) and an amount (mole number) of gas generated by combustion of a gasgenerating agent (A2) is 1 to 20. A1/A2 is preferably 3 to 15, and morepreferably 4 to 10.

[0115] When A1/A2 is not less than 1, delay of rising of an internalpressure of the inflator is prevented, and when A1/A2 is not more than20, an excessive rising of an internal pressure of the inflator isprevented.

[0116] An amount (mole number) of the pressurized gas (A1) is 0.1 to 2.0moles, preferably 0.1 to 1.5 moles and more preferably 0.15 to 1.5moles, while a gas amount (mole number) generated by combustion of thegas generating agent (A2) is 0.01 to 0.2 moles, preferably 0.01 to 0.15moles and more preferably 0.02 to 0.15 moles.

[0117] (4) A ratio B1/B2 of a mass (B1) of pressurized gas (B1) and amass (B2) of a gas generating agent is 1 to 20. B1/B2 is preferably 3 to15, and more preferably 4 to 10.

[0118] When B1/B2 is not less than 1, delay of rising of an internalpressure of the inflator is prevented, and when B1/B2 is not more than20, an excessive rising of an internal pressure of the inflator isprevented.

[0119] The mass (B1) of the pressurized gas is 5 to 80 g, preferably 5to 60 g, more preferably 10 to 60 g. An mass (B2) of the gas generatingagent is described in the requirement (5).

[0120] (5) A mass of a gas generating agent is 0.5 to 30 g. An amount ofthe gas generating agent is preferably 1 to 20 g, more preferably 1 to10 g.

[0121] (6) A charging pressure of pressurized gas is 30,000 to 67,000kPa. The charging pressure of the pressurized gas is preferably 35,000to 60,000 kPa, and more preferably 40,000 to 60,000 kPa.

[0122] When the charging pressure is not less than 30,000 kPa, a gasamount sufficient for inflating an air bag can be secured. When acharging pressure is not more than 67,000 kPa, even with rising of theinternal pressure of the inflator due to combustion of the gasgenerating agent, a sufficient difference between a pressure-resistanceupper limit of the inflator and an internal pressure of the inflator canbe obtained, so that a range in controlling an internal pressure of theinflator can be made wider.

[0123] The inflator of the present invention (III-1) is provided withthe requirements (1) to (6), and each requirement is mutually associatedwith each other. When the initial charging pressure is 60,000 kPa, thesize of the inflator can be reduced by 50 mass % or so at maximum byreducing the width or the diameter and the length in order not to changepressure-resistance of the inflator.

[0124] Further, the inflator of the present invention (III-1) isprovided with the requirements (1) to (6) and the internal pressure ofthe inflator can be controlled more precisely and in a narrower range ascompared with the prior art, by mutually related action of therespective requirements. For this reason, a discharging time of a gasfrom the inflator can be easily controlled and an inflating anddeveloping time of an air bag can be easily adjusted.

[0125] In the present invention (III-1), it is preferable in therequirement (2) that a combustion flame temperature of the gasgenerating agent is not more than 3000° C. The combustion flametemperature means a theoretical value of a flame temperature when thegas generating agent is burnt, and it is obtained by theoreticalcalculation.

[0126] When the combustion flame temperature of the gas generating agentbecomes excessively high, the combustion gas temperature becomes high,and the pressurized gas temperature further becomes excessively high.Thereby, an internal pressure of the inflator rises, and also, atemperature of the gas that flows into the air bag becomes high.However, such a problem is prevented by setting the combustion flametemperature to the above-described temperature or less.

[0127] Further, if the combustion flame temperature exceeds 3000° C.,optimal values (central values) in numerical ranges in the requirements(3) to (6) and the following requirement (7) are shifted such that theair bag inflating action due to combustion gas of the gas generatingagent is decreased, and therefore, the inflator does not function as oneutilizing both the pressurized gas and the combustion gas.

[0128] Also, the combustion flame temperature is related with therequirement (5) in particular. When the inflator is actuated andpressurized gas is discharged outside the inflator, the inside of theinflator is decompressed, so that the temperature lowers and theinternal pressure lowers. In particular, since the combustion flametemperature is as low as not less than 3000° C., there may be a casesuch that it takes too much time for discharging the entire gas becauseof lower gas discharging speed caused by lower internal pressure of theinflator due to the lower temperature. However, by setting the lowerlimit value of an amount of the gas generating agent to not less than 1g, the internal pressure can be prevented from lowering due to lowertemperature inside the inflator (that is, an internal pressure of theinflator can be controlled), so that the air bag can be inflated withinan optimal time. Further, by setting the lower limit value of the gasgenerating agent amount to not less than 1 g, an internal pressure ofthe inflator can be controlled as described above but also a gas amountrequired for inflating an air bag can be supplied. The upper limit valueis a numerical value obtained by considering the volume of a generallyused inflator.

[0129] The combustion flame temperature is more preferably not more than2500° C. and further preferably not more than 2200° C. It is preferablethat the lower limit value of the combustion flame temperature is 900°C.

[0130] In the present invention (III-1) and the like, it is preferablein the requirement (2) that the gas generating agent is a non-azide gasgenerating agent.

[0131] Further, the inventions of the present invention (III-1) and thelike is preferably provided with the requirement (7) such that a ratioA1/C of an amount (mole numbers) of the pressurized gas (A1) and thetotal surface area (cm²) of the gas generating agent (C) is 0.004 to0.05 mole/cm². A1/C is more preferably 0.004 to 0.04 moles, and furtherpreferably 0.004 to 0.03 moles.

[0132] When A1/C is not less than 0.004 mole/cm², a ratio of thepressurize gas amount and the gas generating agent falls in a properrange, and thereby, delay of rising of an internal pressure of theinflator is prevented. (Alternatively, the inflator is prevented frombeing broken due to an excessive rising of an internal pressure of theinflator). When A1/C is not more than 0.05 mole/cm², the ratio of thepressurized gas amount and the gas generating agent falls in the properrange, and thereby, an excessive rising of an internal pressure of theinflator is prevented (alternatively, delay of a rising of an internalpressure of the inflator is prevented.)

[0133] The total surface area (cm²) of the gas generating agent (C) ispreferably 10 to 150 cm², more preferably 20 to 120 cm², and furtherpreferably 30 to 100 cm².

[0134] Further, the present invention (III-1) and the like is preferablyprovided with the requirement (8) such that a ratio C/E of the totalsurface area (cm²) of the gas generating agent (C) and the total area(cm²) of the gas discharging hole (E) is 0.5 to 4. C/E is preferably 0.5to 3.5, and further preferably 0.5 to 3.0.

[0135] When C/E is not less than 0.5, the entire charged pressurized gasis not discharged until combustion of the gas generating agent iscompleted, so that the combustion of the gas generating agent isstabilized. When C/E is not more than 4, an internal pressure of theinflator is maintained in a proper range, and therefore, there is norisk such that the inflator is broken.

[0136] The total area (cm²) of the gas discharging holes (E) ispreferably 5 to 100 cm², more preferably 10 to 80 cm², and furtherpreferably 15 to 60 cm².

[0137] The numerical range of each single requirement shown with A1, A2,B1, B2, C and E is a numerical range suitable in case of eachindependent requirement, and the range of a ratio in case of combiningthe requirements and the numerical range of each single requirement maynot correspond to each other. For example, a ratio of the lower limitvalue or the upper limit value of A1 and the lower limit value or theupper limit value of A2 may not coincide with a ratio of the lower limitvalue or the upper limit value of A1/A2. In order to solve the problemby the invention, a numerical value may be selected from the numericalrange of the respective requirements (A1, A2 and the like) to achieve adesired value within the range of a ratio in case of combining therespective requirements (A1, A2 and the like).

[0138] In the present invention (III-1), the inflator has a pressurizedgas chamber in which an outer shell is formed by a cylindricalpressurized gas chamber housing and is charged with pressurized gas, andan outer diameter of the pressurized gas chamber housing is preferably40 mm or less. The outer diameter of the pressurized gas chamber housingis more preferably not more than 35 mm, and further preferably not morethan 30 mm.

[0139] In the present invention (III-1) and the like, the inflator has apressurized gas chamber in which an outer shell is formed by acylindrical pressurized gas chamber housing and is charged withpressurized gas, and a ratio (L/D) of an outer diameter (D) and a length(L) of the pressurized gas chamber housing is preferably 1 to 10, morepreferably 2 to 10.

[0140] Preferably in the present invention (III-1) and the like, theinflator has a pressurized gas chamber in which an outer shell is formedby a cylindrical pressurized gas chamber housing and is charged withpressurized gas, and the pressurized gas chamber housing is symmetricalregarding the axial and radial directions.

[0141] By making the pressurized gas housing symmetrical, an orientationdoes not have to be determined at a time of assembling, so thatmanufacturing is improved.

[0142] Preferably in the present invention (III-1) and the like, theinflator has a pressurized gas chamber in which an outer shell is formedby a cylindrical pressurized gas chamber housing and is charged withpressurized gas, and the pressurized gas chamber housing is symmetricalregarding the axial and radial directions and both end sides thereof arereduced in diameter. That “both ends side are reduced in diameter” meansthat diameters at both ends of the pressurized gas chamber housing aremade smaller than diameters of the other portion thereof.

[0143] By making the pressurized gas housing symmetrical, an orientationdoes not have to be determined at a time of assembling, so thatmanufacturing is improved. Further, when both ends are reduced indiameter, joining to another member can be facilitated, in particular,manufacturing in case of joining with resistance-welding is improved.

[0144] Preferably in the present invention (III-1) and the like, theinflator has a pressurized gas chamber in which an outer shell is formedby a cylindrical pressurized gas chamber housing and is charged withpressurized gas, and a pressurized gas charging hole is formed in a sidesurface of the pressurized gas chamber housing, and the hole is closedby a pin after the pressurized gas is charged.

[0145] Since the pressurized gas charging hole is formed and closed bythe pin in this manner, another members can be connected to both endsides of the pressurized gas chamber housing.

[0146] Preferably in the present invention (III-1) and the like, the pinis protruding into the pressurized gas chamber housing and a protrudingportion thereof has such a length that combustion gas flow of the gasgenerating agent strikes against the protruding portion. By taking suchan aspect, it is possible to make combustion residue strike against andadhere to the pin, so that the combustion chamber can be arrested:

[0147] Preferably in the present invention (III-1) and the like, theinflator has a pressurized gas chamber in which an outer shell is formedby a cylindrical pressurized gas chamber housing and is charged withpressurized gas, a gas generator in which an outer shell is formed by agas generator housing and the ignition means and the gas generatingagent are accommodated, and a diffuser portion, wherein

[0148] the gas generator housing is connected to one end of thepressurized gas chamber housing and the diffuser portion is connected tothe other end of the pressurized gas housing, and

[0149] a first rupturable plate closes between the pressurized gaschamber and the gas generator and a second rupturable plate closesbetween the pressurized gas chamber and the diffuser portion.

[0150] Preferably in the present invention (III-1) and the like, a caphaving a gas ejecting hole provided on at least one of a side surfaceand an end surface thereof, particularly on the side surface covers thefirst rupturable plate from the pressurized gas chamber side. Bydisposing such a cap, a arresting effect for the combustion residue isenhanced.

[0151] Preferably in the present invention (III-1) and the like, the gasgenerator housing and the pressurized gas chamber housing, and thediffuser portion and the pressurized gas chamber housing are connectedby resistance-welding.

[0152] Preferably in the present invention (III-1) and the like, outerdiameters of the pressurized gas chamber housing, the gas generatorhousing and the diffuser portion are equal or approximate to oneanother.

[0153] In the present invention (III-15), the inflator has a pressurizedgas chamber in which an outer shell is formed by a cylindricalpressurized gas chamber housing and is charged with pressurized gas, agas generator in which an outer shell is formed by a gas generatorhousing and the ignition means and the gas generating agent areaccommodated, and a diffuser portion, wherein

[0154] the gas generator housing is connected to one end of thepressurized gas chamber housing and the diffuser portion is connected tothe other end of the pressurized gas housing, and

[0155] a first rupturable plate closes between the pressurized gaschamber and the gas generator and a second rupturable plate closesbetween the pressurized gas chamber and the diffuser portion, and outerdiameters of the pressurized gas chamber housing, the gas generatorhousing and the diffuser portion are equal or approximate to oneanother.

[0156] This is an inflator in which an air bag is inflated by usingpressurized gas, the pressurized gas is charged in a pressurized gaschamber having a outer shell formed by a cylindrical pressurized gaschamber housing,

[0157] wherein the pressurized gas chamber housing is symmetricalregarding the axial and a radial directions, and both ends thereof arereduced in diameter.

[0158] That “both ends side are reduced in diameter” means thatdiameters at both ends of the pressurized gas chamber housing are madesmaller than diameters of the other portion thereof.

[0159] By making the pressurized gas housing symmetrical, an orientationdoes not have to be determined at a time of assembling, so thatmanufacturing is improved. Further, when both ends are reduced indiameter, joining to another member can be facilitated, in particular,manufacturing in case of joining with resistance-welding is improved.

[0160] Preferably in the present invention (III-15), an inflator usescombustion gas obtained by combustion of a gas generating agent togetherwith pressurized gas as a inflating means for an air bag, wherein

[0161] the inflator has a pressurized gas chamber in which an outershell is formed by a cylindrical pressurized gas chamber housing and ischarged with pressurized gas, a gas generator for generating acombustion gas and a diffuser portion having a gas discharging port, andthe pressurized gas chamber housing is symmetrical regarding the axialand radial directions and both end sides thereof are reduced indiameter.

[0162] Preferably in the above-described invention, a gas generator inwhich an outer shell is formed by a gas generator housing and theignition means and the gas generating agent are accommodated,

[0163] the gas generator housing is connected to one end of thepressurized gas chamber housing and the diffuser portion is connected tothe other end of the pressurized gas housing, and

[0164] a first rupturable plate closes between the pressurized gaschamber and the gas generator and a second rupturable plate closesbetween the pressurized gas chamber and the diffuser portion.

[0165] In this invention, combustion gas generated inside the gasgenerator flows in the pressurized gas chamber after the firstruptruable plate is broken, and thereafter the combustion gas isdischarged from the gas discharging hole of the diffuser portiontogether with the pressurized gas after the second rupturable plate isbroken, thereby inflating an air bag.

[0166] Preferably in the above-described invention, one or both of a setof the gas generator housing and the pressurized gas chamber housing,and a set of the diffuser portion and the pressurized gas chamberhousing are connected by resistance-welding.

[0167] Preferably in the present invention (III-15), an inflatorsubstantially uses only pressurized gas as an inflating means for an airbag, and

[0168] the inflator comprises a pressurized gas chamber in which anouter shell is formed by a cylindrical pressurized gas chamber housingand pressurized gas is charged, and a diffuser portion which isconnected to the pressurized gas chamber and has a gas discharging hole,a rupturable plate closing between the pressurized gas chamber and thediffuser portion, and an igniter accommodated inside the diffuserportion as a rupturable means of the rupturable plate,

[0169] the pressurized gas chamber housing is symmetrical regarding theaxial and radial directions and both ends thereof are reduced indiameter.

[0170] In this invention, the rupturable plate is broken by actuation ofthe igniter (an electrical type igniter provided with a priming) and thepressurized gas is discharged from the gas discharging hole of thediffuser portion, thereby inflating the air bag. Combustion gas of thepriming is slightly generated by actuation of the igniter, but thiscombustion gas itself does not substantially participate in inflation ofthe air bag, so that the inflating means for the air bag issubstantially only the pressurized gas.

[0171] Preferably in the above-described invention, a cylindrical gasdischarging port connected to the gas discharging hole of the diffuserportion is provided, the gas discharging port is mounted to coincidewith the axial direction of the pressurized gas chamber housing, and thepressurized gas discharged from the gas discharging hole passes throughthe gas discharging port and is discharged from an opening provided inthe gas discharging port to inflate the air bag.

[0172] By providing such a gas discharging port, the axial direction ofthe pressurized gas chamber housing and the discharging direction of thepressurized gas coincide with each other, and the axial direction of thepressurized gas chamber housing and an inflating direction of the airbag coincide with each other, so that mounting an air bag isfacilitated.

[0173] Preferably in the above-described invention, the diffuser portionand the pressurized gas chamber housing are connected byresistance-welding.

[0174] Also, the present invention (III-22) provides an air bag systemcomprising an activation-signal outputting means comprising an impactsensor and a control unit, and a module case in which any one of theabove-described inflators and an air bag are accommodated.

[0175] The present invention (III-22) is an inflator in which an air bagis inflated by using pressurized gas, the pressurized gas is charged ina pressurized gas chamber having an outer shell formed by a cylindricalpressurized gas chamber housing, the pressurized gas chamber housing issymmetrical regarding the axial and radial directions and both endsthereof are reduced in diameter, only the pressurized gas issubstantially used as an inflating means for an air bag, wherein

[0176] the inflator comprises a pressurized gas chamber having an outershell formed by a cylindrical pressurized gas chamber housing, and apressurized gas charged inside the pressurize gas chamber, a diffuserportion connected to the pressurized gas chamber and having a gasdischarging hole, a rupturable plate closing the pressurized gas chamberand the diffuser portion, and an igniter accommodated inside thediffuser portion as a rupturing means for the rupturable plate,

[0177] the pressurized gas chamber housing is symmetrical regarding theaxial and radial directions, and both ends thereof are reduced indiameter,

[0178] a cylindrical gas discharging port connected to the gasdischarging hole of the diffuser portion is provided, the gasdischarging port is mounted to coincide with the axial direction of thepressurized gas chamber housing, and pressurized gas discharged from thegas discharging hole passes through the gas discharging port and isdischarged from an opening provided in the gas discharging port toinflate an air bag, and

[0179] the diffuser portion and the pressurized gas chamber housing areconnected by resistance-welding.

[0180] It is preferable that the gas generating agent used in thisinvention is non-azide gas generating agents, and the gas generatingagent can be decided in relation to composition of the pressurized gasas follows.

[0181] As the gas generating agent, for example, it is possible to use amaterial including fuel and oxidizing agent, or fuel, oxidizing agentand slag-forming agent, being mixed with binder if required, and formedinto a desired shape. If such a gas generating agent is used, a gasgenerated by combustion of the agent can be used for inflating anddeveloping an air bag together with the pressurized medium. Especially,when the gas generating agent including(the slag-forming agent is used,slag is easily made, so that an amount of mist-like combustion residuesdischarged from the inflator can be largely reduced. However, in case ofreducing a charged amount of gas generating agent and generatedresidues, it is unnecessary to use a slag-forming agent.

[0182] An example of the fuel can be one or at least two selected fromthe group consisting of triazine derivatives, tetrazole derivatives,triazole derivatives, guanidine derivatives, azodicarbonamidederivatives, and hydrazine derivatives are preferably used.

[0183] As triazine derivatives, one or at least two selected from thegroup consisting of triazine (1, 2, 3-triazine, 1, 2, 4-triazine, 1, 3,5-triazine), melamine, trihydrazinotriazine, trimethylol melamine,alkylated methylol melamine, cyanuric acid derivatives such as ammeline,ammelide, ammeland, cyanuric acid or cyanurate esters, a nitric acidsalt of melam, melem or melamine, a perchloric acid salt of melamine andnitro-melamine compound such as dinitroameline.

[0184] An example of tetrazole derivatives, triazole derivates,azodicarbonamide derivates and hydrazine derivates can be one or atleast two selected from the group consisting of 5-oxo-1, 2, 4-triazole,tetrazole, 5-aminotetrazole, 5, 5′-bi-1H-tetrazole, biuret,azodicarbonamide, carbohydrazide, carbohydrazide nitrate complex,dihydrazide oxalate and hydrazine-nitrate complex.

[0185] An example of guanidine derivatives can be one or at least twoselected from the group consisting of nitroguanidine (NQ), guanidinenitrate (GN), guanidine carbonate, aminonitroguanidine, aminoguanidinenitrate, aminoguanidine carbonate, diaminoguanidine nitrate,diaminoguanidine carbonate, triaminoguanidine nitrate and the like.

[0186] As the oxidizing agent, one or at least two selected from thegroup consisting of strontium nitrate, potassium nitrate, ammoniumnitrate, potassium perchlorate, copper oxide, ferrous oxide, a basiccopper nitrate are preferably used.

[0187] As the slag-forming agent, one or at least two selected from thegroup consisting of acid clay, talc, bentonite, diatomaceous earth,kaolin, silica, alumina, sodium silicate, silicone nitride, siliconcarbide, hydrotalsite, and a mixture thereof are preferably used.

[0188] As the bonding agent, one or at least two selected from the groupconsisting of sodium salt of carboxymethylcellulose, hydroxyethylcellulose, starch, polyvinyl alcohol, guar gum, microcrystal cellulose,polyacrylamide and calcium stearate are preferably used.

[0189] The gas generating agent used in the present invention caninclude 20 to 60 mass % of nitroguanidine as the fuel and 80 to 40 mass% of the oxidizing agent, and preferably, 30 to 40 mass % ofnitroguanidine as the fuel and 70 to 60 mass % of strontium nitrate asthe oxidizing agent. Further, the bonding agent (sodiumcarboxymethylcellulose or the like) and the slag-forming agent (acidclay or the like) can further be mixed in addition to the fuel and theoxidizing agent. In this case, it is preferable that the fuel is 20 to60 mass %, the oxidizing agent is 40 to 65 mass %, the bonding agent is3 to 12 mass % (preferably 4 to 12 mass %), and the slag-forming agentis 1 to 20 mass % (preferably 3 to 7 mass %).

[0190] According to the inflator of the present invention, the inflatorcan be compact while securing a charged amount of pressurized gasapproximately equal to that in the conventional inflator. Also in thatcase, an internal pressure of the inflator can be controlledappropriately at a time of actuation, so that an inflating performanceof an air bag can be maintained in an optimal state.

BRIEF DESCRIPTION OF THE DRAWINGS

[0191]FIG. 1 is a sectional view of an inflator in the axial direction.

[0192]FIG. 2 is a sectional view of an inflator in the axial direction.

[0193]FIG. 3 is a sectional view of an inflator in the axial direction.

[0194]FIG. 4 is a perspective view and a plan view of a cap used in aninflator.

[0195]FIG. 5 is a perspective view and a plan view of a cap used in aninflator.

[0196]FIG. 6 is a perspective view of a cap used in an inflator.

[0197]FIG. 7 is a sectional view of an inflator in the axial direction.

[0198]FIG. 8 is a sectional view of an inflator in the axial direction.

[0199]FIG. 9 is a sectional view of an inflator in the axial direction.

[0200]FIG. 10 is a sectional view of an inflator in the axial direction.

[0201]FIG. 11 is a sectional view of an inflator in the axial direction.

[0202]FIG. 12 is a sectional view of an inflator in the axial direction.

[0203]FIG. 13 is a sectional view of an inflator in the axial direction.

[0204]FIG. 14 is a sectional view of an inflator in the axial direction.

[0205]FIG. 15 is a sectional view of an inflator in the axial direction.

[0206]FIG. 16 is a sectional view of an inflator in the axial direction.

[0207]FIG. 17 is a sectional view of an inflator in the axial direction.

[0208]FIG. 18 is a sectional view of an inflator in the axial direction.

[0209]FIG. 19 is a sectional view of an inflator in the axial direction.

[0210]FIG. 20 is a sectional view of an inflator in the axial direction.

[0211]FIG. 21 is a sectional view of an inflator in the axial direction.

[0212]FIG. 22 is a tank curve obtained in a 60-liters tank combustiontest conducted in Example 1.

[0213] Reference numerals in the drawings will be explained.

[0214]10 inflator

[0215]20 pressurized medium chamber or a pressurized gas chamber

[0216]22 pressurized medium chamber housing or a pressurized gas chamberhouisng

[0217]30 gas generator

[0218]32 gas generator housing

[0219]35 crimped portion

[0220]34 igniter

[0221]36 gas generating agent

[0222]40 first rupturable plate

[0223]42 gas ejecting hole

[0224]44 cap

[0225]48 crimped portion

[0226]50 diffuser portion

[0227]51 closed end surface

[0228]52 gas discharging hole

[0229]58 second rupturable plate

[0230] Embodiment of Invention (I)

[0231] Embodiment 1

[0232] One embodiment will be explained with reference to FIG. 1. FIG. 1is a sectional view of an inflator in the axial direction thereof.

[0233] An inflator 10 comprises a pressurized medium chamber 20, a gasgenerator 30 and a diffuser portion 50.

[0234] The pressurized medium chamber 20 has an outer shell formed by acylindrical pressurized medium chamber housing 22 and it is charged witha pressurized medium comprising a mixture of argon and helium. Since thepressurized medium chamber housing 22 is made symmetrical in the axialdirection and a radial direction thereof, it is unnecessary to adjustthe orientation in the axial and radial directions at a time ofassembling.

[0235] A charging hole 24 of a pressurized medium is formed on a sidesurface of the pressurized medium chamber housing 22, and it is closedby a pin 26 after the pressurized medium is charged. A distal endportion 26 a of the pin 26 protrudes into the pressurized medium chamber20, and the protruding portion thereof has such a length that combustiongas flow of a gas generating agent strikes against the protrudingportion. By adjusting the length of the protruding portion of the pin26, combustion gas can strike against the pin 26 to have combustionresidues adhered to the pin 26. In FIG. 1, the pin 26 can be extendeduntil the distal end portion 26 a thereof abuts against the oppositewall surface 22 a.

[0236] The gas generator 30 includes an ignition means (an electricaltype igniter) 34 and a gas generating agent 36 accommodated in a gasgenerator housing 32, and it is connected to one end of the pressurizedmedium chamber 20. The gas generator housing 32 and the pressurizedmedium chamber housing 22 are connected at a connecting portion 49 byresistance-welding. When the inflator 10 is assembled in an air bagsystem, the ignition means 34 is connected to an external power sourcevia a connector and a lead wire.

[0237] The gas generating agent 36 can comprises, for example, 34 mass %of nitroguanidine as a fuel, 56 mass % of strontium nitrate as anoxidizing agent, and 10 mass % of sodium carboxymethylcellulose as abonding agent (a discharged gas temperature: 700 to 1630° C.). Acombustion residue generated when the gas generating agent 36 of theabove composition is burnt is strontium oxide (melting point: 2430° C.).For this reason, the combustion residue is solidified to be massive(slag-like) without being melted.

[0238] A first communication hole 38 between the pressurized mediumchamber 20 and the gas generator 30 is closed by a first rupturableplate 40 transformed into a bowl-like shape due to a pressure of thepressurized medium, and the interior of the gas generator 30 ismaintained in the normal pressure. The first rupturable plate 40 isresistance-welded to the gas generator housing 32 at a peripheral edgeportion 40 a.

[0239] A cap 44 having gas ejecting holes 42 is covered over the firstrupturable plate 40 from the pressurized medium chamber 20 side. The cap44 is attached to cover the first rupturable plate 40, so thatcombustion gas generated by combustion of the gas generating agent 36 isalways ejected from the gas ejecting holes 42 via the cap 44.

[0240] The cap 44 has a flange portion 46 formed by folding an openingperipheral edge portion outwardly, and it is fixed by crimping a portion(a crimping portion) 48 of the gas generator housing 32 at the flangeportion 46.

[0241] A diffuser portion 50 having gas discharging holes 52 fordischarging the pressurized medium and the combustion gas is connectedto the other end side of the pressurized medium chamber 20, and thediffuser portion 50 and the pressurized medium chamber housing 22 isresistance-welded to each other at a connecting portion 54. A filtermade of wire mesh can be disposed inside the diffuser portion 50 inorder to arrest the combustion residue, if required.

[0242] A second communication hole 56 between the pressurized mediumchamber 20 and the diffuser portion 50 is closed by a second rupturableplate 58 transformed into a bowl-like shape due to pressure of thepressurized medium, and the interior of the diffuser portion 50 ismaintained in the normal pressure. The second rupturable plate 58 isresistance-welded to the diffuser portion 50 at a peripheral edgeportion 58 a.

[0243] Next, an operation in case of the inflator 10 shown in FIG. 1which is incorporated to an air bag system mounted to an automobile willbe explained.

[0244] When an automobile receives the impact by a collision, theigniter 34 is actuated and ignited by the activation-signal outputtingmeans to burn the gas generating agent 36, thereby generating a hightemperature combustion gas. At this time, since the melting point of acombustion residue generated by combustion of the gas generating agent36 is equal to or more than a discharging temperature of a gas generatedfrom the gas generating agent 36, the combustion residue can hardlymelt, being maintained solid.

[0245] Thereafter, the first rupturable plate 40 is broken by a pressurerise inside the gas generator 30 due to the high temperature combustiongas, and combustion gas including a combustion residue flows into thecap 44 to be ejected from the gas ejecting holes 42. At this time, sincea temperature difference between the pressurized medium and thecombustion gas in the pressurized medium chamber 20 is large, thecombustion gas is cooled rapidly, so that the high temperaturecombustion residue is cooled and solidified and a combustion residuealso adheres to an inner wall surface of an end surface 44 a of the cap44. Further, since the combustion gas ejected strikes against an innerwall 22 a of the pressurized medium chamber housing 22, the combustionresidue adheres to an inner wall surface and it can be hardly dischargedout of the inflator 10. Incidentally, part of the remaining combustionresidue adheres to the pin 26, too.

[0246] Thereafter, since the second rupturable plate 58 is broken by apressure rise inside the pressurized medium chamber 20, the pressurizedmedium and the combustion gas are discharged from the gas dischargingholes 52 via the second communication hole 56 to inflate an air bag.

[0247] In such a course of the operation, since the inflator 10 exhibitsthe above-described actions and effects (1) to (3), the combustionresidue discharged into the air bag is largely suppressed by thesemutual effects. In an actual measurement, in case of the inflator of thestructure shown in FIG. 1 in which the cap 44 is not provided, thecombustion residue discharged outside the inflator 10 was 700 mg, but itcould be reduced to 200 mg with the structure shown in FIG. 1. Further,as shown in FIG. 2, by providing a cap 64 in the second rupturable plate58 side, the arresting performance of the combustion residue can befurther increased. Reference numeral 62 denotes a gas ejecting hole,reference numeral 68 denotes a flange portion, and the cap 64 can befixed to the diffuser portion 50 by the flange portion 68 and thecrimping portion 59.

[0248] Embodiment 2

[0249] Another embodiment will be explained with reference to FIG. 3.FIG. 3 is a sectional view of an inflator in the axial directionthereof. An inflator 100 shown in FIG. 3 has almost the same structureas the inflator 10 shown in FIG. 1, and, in FIG. 3, the same referencenumerals as those in FIG. 1 denote the same parts. A difference instructure from FIG. 1 and a difference in advantageous effect due to thedifference in structure will be explained below.

[0250] In the inflator 100 shown in FIG. 3, an inner wall surface 22 aof a pressurized medium chamber housing 22 has a groove with a depth of0.2 mm formed continuously or discontinuously in the circumferentialdirection. With this, a combustion residue in combustion gas is caughtand captured in the groove, an advantageous effect (4) can be exhibitedin addition to the advantageous effects (1) to (3) Further, as shown inFIG. 2, an aspect in which a cap 64 is provided can be employed.

[0251] Embodiment 3

[0252] Another embodiment will be explained with reference to FIG. 4.FIG. 4 is a sectional view of an inflator in the axial directionthereof. An inflator 200 shown in FIG. 4 has almost the same structureas that of the inflator 10 shown in FIG. 1, and, in FIG. 4, the samereference numerals as those in FIG. 1 denote the same parts. Adifference in structure from FIG. 1 and a difference in advantageouseffect due to the difference in structure will be explained below.

[0253] In an inflator 200 shown in FIG. 4, gas ejecting holes 42 areprovided on a side surface of a cap 44 and they are opened to ejectcombustion gas towards the gas generator 30. With this, combustion gasejected from the gas ejecting holes 42 strikes against a crimped portion48 and its vicinities before it strikes against the inner wall surface22 a of the pressurized medium chamber housing 22, and thereby, anadvantageous effect (5) can be exhibited in addition to the advantageouseffects (1) to (3). Incidentally, when the aspect shown in FIG. 3 isemployed with respect to the inner wall surface 22 a of the pressurizedmedium chamber housing 22, the advantageous effect (4) can be furtherexhibited. Also, as shown in FIG. 2, the aspect in which the cap 64 isprovided can be employed, and the cap 44 of the other embodiment can beused instead of the cap 64.

[0254] Embodiment 4

[0255] Another embodiment will be explained with reference to FIG. 5 toFIG. 7. FIG. 5 is a perspective view and a plan view of a cap of oneembodiment, FIG. 6 is a perspective view and a plan view of a cap ofanother embodiment, and FIG. 7 is a perspective view of a cap of anotherembodiment. A cap 44 shown in FIG. 5 to FIG. 7 can be disposed into theinflators 10, 100 and 200 shown in FIG. 1, FIG. 3 and FIG. 4respectively, and, in the inflator shown in FIG. 2, the cap 64 can be inthe shapes shown in FIG. 5 to FIG. 7.

[0256] In the cap 44 shown in FIG. 5, gas ejecting holes 42 are providedon a side surface of the cap 44 a, and a member (restricting member) 45for circumferentially restricting an ejecting direction of combustiongas from the gas ejecting holes 42. The restricting member 45 is formedin a L-letter shape in plan view. Incidentally, the orientation of therestricting member 45 may be a different direction from that in FIG. 5.

[0257] Since such restricting members 45 are provided, combustion gasejected from the gas ejecting hole 42 is ejected in the direction alongthe circumferential surface of the cap 44 to form an eddy, so that theadvantageous effect (5) can be exhibited in addition to the advantageouseffects (1) to (3). Incidentally, when the shape shown in FIG. 3 can beemployed for the inner wall surface 22 a of the pressurized mediumchamber housing 22, the advantageous effect (4) can be furtherexhibited.

[0258] The cap 44 shown in FIG. 6 is provided with flat plate-shapedrestricting members 45 instead of the L-letter-shaped restrictingmembers 45 shown in FIG. 5, and the same advantageous effect as those inFIG. 5 can be obtained.

[0259] The cap 44 shown in FIG. 7 is provided on its end surface 44 bwith gas ejecting holes 42, and members (restricting members) 45 forcircumferentially restricting an ejected direction of combustion gasfrom the gas ejecting holes 42. The restricting member 45 can be formedin the same shape as shown in FIG. 5 or FIG. 6. An inflator using thecap 44 shown in FIG. 7 can obtain the same advantageous effects as thosein FIG. 5 and FIG. 6.

[0260] Embodiment 5

[0261] Another embodiment will be explained with reference to FIG. 8.FIG. 8 is a sectional view of an inflator in the axial direction. Aninflator 300 shown in FIG. 8 has almost the same structure as that ofthe inflator 10 shown in FIG. 1, and, in FIG. 8, the same referencenumerals as these in FIG. 1 denote the same parts. A difference instructure from FIG. 1 and a difference in advantageous effect due to thedifference in structure will be explained below.

[0262] In the inflator 300 shown in FIG. 8, a cylindrical barrier member310 is attached thereto. The barrier member 310 has a closed one endintegrated with a end surface of the cap 44 b and the other end opened,and it is formed such that a side wall 311 faces gas ejecting holes 42provided on the side surface of the cap 44 a with a distance. Also, asshown in FIG. 2, the aspect in which the cap 64 is provided can beemployed, and further, the cap 44 of the other embodiment can beemployed instead of the cap 64.

[0263] With such a barrier member 310, the combustion gas ejected fromthe gas ejecting holes 42 strikes against an inner wall of a side wall311 of the barrier member, and then, it moves from the opening. Thereby,the advantageous effect (6) can be exhibited in addition to theadvantageous effects (1) to (3). Incidentally, when the aspect shown inFIG. 3 is employed with respect to the inner wall surface 22 a of thepressurized medium chamber housing 22, the advantageous effect (4) canbe exhibited as well.

[0264] Embodiment 6

[0265] Another embodiment will be explained with reference to FIG. 9.FIG. 9 is a sectional view of an inflator in the axial direction. Aninflator 400 shown in FIG. 9 has almost the same structure as that ofthe inflator 10 shown in FIG. 1, and, in FIG. 9, the same referencenumerals as those in FIG. 1 denote the same parts. A difference instructure from FIG. 1 and a difference in advantageous effect due to thedifference in structure will be explained below.

[0266] In the inflator 400 shown in FIG. 9, a disk-like barrier member410 is attached. The barrier member 410 is integrated with a end surfaceof the cap 44 b and it is extended from the end surface of the cap 44 btowards an inner wall surface 22 a of the pressurized medium chamberhousing 22. Also, as shown in FIG. 2, the aspect in which the cap 64 isprovided can be employed, and further, the cap 44 of another embodimentcan be used instead of the cap 64.

[0267] With such a barrier member 410, combustion gas ejected from thegas ejecting holes 42 strikes against the barrier member 410, and then,it moves from a clearance between the inner wall surface 22 a of thepressurized medium chamber housing 20 and an peripheral edge portion 411of the barrier member. Thereby, the advantageous effect (6) can beexhibited in addition to the advantageous effects (1) to (3).Incidentally, when the aspect shown in FIG. 3 is employed with respectto the inner wall surface 22 a of the pressurized medium chamber housing22, the advantageous effect (4) can further be exhibited.

[0268] Embodiment 7

[0269] Another embodiment will be explained with reference to FIG. 10.FIG. 10 is a sectional view of an inflator in the axial direction. Aninflator 500 shown in FIG. 10 has almost the same structure as that ofthe inflator 10 shown in FIG. 1, and, in FIG. 10, the same referencenumerals as those in FIG. 1 denote the same parts. A difference instructure in FIG. 1 and a difference in advantageous effect due to thedifference in structure will be explained below.

[0270] In the inflator 500 shown in FIG. 10, a disk-like barrier member510 is attached. The barrier member 510 is integrated with an endsurface of the cap 44 b, and it is extended from the end surface of thecap 44 b towards the inner wall surface 22 a of the pressurized mediumchamber housing 20 so that a peripheral edge portion 511 abuts on theinner wall surface 22 a. Gas passing ports 512 and restricting means 513having similar shapes like those in FIG. 6 are provided in theperipheral edge portion 511. Also, as shown in FIG. 2, the aspect inwhich the cap 64 is provided can be employed and further, the cap 44 ofanother embodiment can be used instead of the cap 64.

[0271] With such a barrier member 510, combustion gas ejected from thegas ejecting holes 42 strikes against the barrier member 510, and then,it moves through the gas passing ports 512 and the restricting means513. Thereby, the advantageous effects (6) and (5) can be exhibited inaddition to the advantageous effects (1) to (3). Incidentally, when theaspect shown in FIG. 3 is employed with respect to the inner wallsurface 22 a of the pressurized medium chamber housing 22, theadvantageous effect (4) can further be exhibited.

[0272] The inflator of the present invention can be applied to variousinflators such as an air bag inflator for a driver side, an air baginflator for a passenger side next to a driver, an air bag inflator fora side collision, an inflator for a curtain air bag, an inflator for aknee-bolster, an inflator for an inflatable seat belt, an inflator for atubular system, an iflator for a pretensioner and the like.

[0273] Embodiments of Invention (II)

[0274] (1) Embodiment 1

[0275] One embodiment will be explained with reference to FIG. 11. FIG.1 is a sectional view of an inflator in the axial direction.

[0276] An inflator 610 comprises a pressurized gas chamber 620, a gasgenerator 630 and a diffuser portion 650.

[0277] The pressurized gas chamber 620 has an outer shell formed by acylindrical pressurized gas chamber housing 622 and it is charged withpressurized gas comprising a mixture of argon and helium. Since thepressurized gas chamber housing 622 is made symmetrical in the axialdirection and a radial direction thereof, it is unnecessary to adjustthe orientation in the axial and radial directions at a time ofassembling.

[0278] A charging hole 624 of pressurized gas is formed on a sidesurface of the pressurized gas chamber housing 622, and it is closed bya pin 626 after the pressurized gas is charged. A distal end portion 626a of the pin 626 protrudes into the pressurized gas chamber 620, and theprotruding portion thereof has such a length that combustion gas flow ofa gas generating agent strikes against the protruding portion. Byadjusting the length of the protruding portion of the pin 626,combustion gas can strike against the pin 26 to have combustion residuesadhered to the pin 626. In FIG. 11, the pin 626 can be extended untilthe distal end portion 626 a thereof abuts against the opposite wallsurface 622 a.

[0279] The gas generator 630 has an ignition means (an electrical typeigniter) 634 accommodated in a gas generator housing 632 and a gasgenerating chamber 635 accommodating a gas generating agent 636, and itis connected to one end of the pressurized gas chamber 620. A retainer639 is disposed inside the gas generating chamber 635.

[0280] The gas generator housing 632 and the pressurized gas chamberhousing 622 are connected at a connecting portion 649 byresistance-welding. When the inflator 600 is assembled in an air bagsystem, the ignition means 634 is connected to an external power sourcevia a connector and a lead wire.

[0281] The gas generating agent 636 can comprises, for example, 34 mass% of nitroguanidine as a fuel, 56 mass % of strontium nitrate as anoxidizing agent, and 10 mass % of sodium carboxymethylcellulose as abonding agent (a discharged gas temperature: 700 to 1630° C.). Acombustion residue generated when the gas generating agent 636 of theabove composition is burnt is strontium oxide (melting point: 2430° C.)For this reason, the combustion residue is solidified to be massive(slag-like) without being melted.

[0282] A first communication hole 638 between the pressurized gaschamber 620 and the gas generator 630 is closed by a first rupturableplate 640, and the interior of the gas generator 630 is maintained inthe normal pressure. The first rupturable plate 640 is resistance-weldedto the gas generator housing 632 at a peripheral edge portion.

[0283] A diffuser portion 650 having gas discharging ports 652 fordischarging the pressurized gas and the combustion gas is connected tothe other end side of the pressurized gas chamber 620, and the diffuserportion 650 and the pressurized gas chamber housing 622 areresistance-welded to each other at a connecting portion 654. Thediffuser portion 650 and the gas generating chamber housing 622 areconnected such that their central axes coincide with each other.

[0284] The diffuser portion 650 is a cap-shaped one having a pluralityof gas discharging ports 652 through which a gas passes, wherein adistance L between a closed end surface 651 and an gas discharging portnearest to the closed end surface 651 and a diameter D of the rupturableplate 658 (except for a welded peripheral edge portion) satisfy thefollowing formula: L≧D/2.

[0285] The distance L is preferably 3 to 8 mm, more preferably 4 to 8mm, and particularly preferably 5 to 8 mm. The diameter of a pluralityof the gas discharging ports 652 is preferably 0.5 to 2 mm, and morepreferably 0.5 to 1.2 mm. The total opening area of a plurality of thegas discharging ports 652 is preferably 20 to 1000 mm², and morepreferably 100 to 500 mm².

[0286] A second communication hole 656 between the pressurized gaschamber 620 and the diffuser portion 650 is closed by a secondrupturable plate 658, and the interior of the diffuser portion 650 ismaintained in the normal pressure. The second rupturable plate 658 isresistance-welded to the diffuser portion 650 at its peripheral edgeportion.

[0287] Next, an operation in case of the inflator 600 shown in FIG. 11which is incorporated to an air bag system mounted to an automobile willbe explained.

[0288] When an automobile receives the impact by a collision, theigniter 634 is actuated and ignited by the activation-signal outputtingmeans to burn the gas generating agent 636, thereby generating a hightemperature combustion gas. At this time, since the melting point of acombustion residue generated by combustion of the gas generating agent636 is equal to or more than a discharging temperature of a gasgenerated from the gas generating agent 636, the combustion residue canhardly melt, being maintained solid.

[0289] Thereafter, the first rupturable plate 640 is broken by apressure rise inside the gas generator 630 due to the high temperaturecombustion gas, and combustion gas including a combustion residue flowsinto the pressurized gas chamber 620.

[0290] At this time, since a temperature difference between thepressurized gas and the combustion gas in the pressurized gas chamber620 is large, the combustion gas is cooled rapidly, so that the hightemperature combustion residue is cooled and solidified. And, since thecombustion gas also strikes against an inner wall 622 a of thepressurized gas chamber housing 622, the combustion residue adheres toan inner wall surface thereof and it can be hardly discharged out of theinflator 600. Incidentally, part of the remaining combustion residueadheres to the pin 626, too.

[0291] Thereafter, since the second rupturable plate 658 is broken by apressure rise inside the pressurized gas chamber 620, the pressurizedgas and the combustion gas are discharged from the gas discharging holes652 via the second communication hole 656 to inflate an air bag.

[0292] At this time, since the combustion gas and the pressurized gasflow out from the gas discharging ports 652 after they once strikesagainst the closed end surface 651 of the diffuser portion 650 to changetheir flow directions, foreign materials can easily remain in a pocketportion from the closed end surface 651 to the gas discharging hole 652nearest therefrom. And, since the above action is elevated by setting adepth (L) of the pocket portion to the maximum length (D/2) of theforeign material or more, the foreign material can remain more easily.Due to that the gas is discharged via the diffuser portion 650 in thismanner, the foreign materials are removed.

[0293] In such a course of the operation, since the inflator 600exhibits the above-described advantageous effects (IIa) to (IIc), (1) to(3), an amount of pieces of the broken rupturable plate or combustionresidues discharged into the air bag is largely suppressed by thesemutual effects.

[0294] (2) Embodiment 2

[0295] One embodiment will be explained with reference to FIG. 12. FIG.12 is a sectional view of an inflator in the axial direction. Since theinflators shown in FIG. 12 and FIG. 11 are different from each otheronly in part of a structure of a diffuser portion, the same parts areattached with the same reference numerals and explanations thereof willbe omitted.

[0296] An inflator 700 shown in FIG. 12 is provided at a distal endportion of a diffuser portion 650 with a stud bolt 660 used at the timeof mounting the inflator to a module case.

[0297] The inflator 700 shown in FIG. 12 discharges a gas according tothe same action as that of the inflator 600 shown in FIG. 11 andconducts the same operation.

[0298] (3) Embodiment 3

[0299] One embodiment will be explained with reference to FIG. 13. FIG.13 is a sectional view of an inflator in the axial direction thereof.

[0300] An inflator 10 comprises a pressurized gas chamber 20, a gasgenerator 30 and a diffuser portion 50.

[0301] The pressurized gas chamber 20 has an outer shell formed by acylindrical pressurized gas chamber housing 22 and it is charged withpressurized gas comprising a mixture of argon and helium. Since thepressurized gas chamber housing 22 is made symmetrical in the axialdirection and a radial direction thereof, it is unnecessary to adjustthe orientation in the axial and radial directions at a time ofassembling.

[0302] A charging hole 24 of pressurized gas is formed on a side surfaceof the pressurized gas chamber housing 22, and it is closed by a pin 26after the pressurized gas is charged. A distal end portion 26 a of thepin 26 protrudes into the pressurized gas chamber 20, and the protrudingportion thereof has such a length that combustion gas flow of a gasgenerating agent strikes against the protruding portion. By adjustingthe length of the protruding portion of the pin 26, combustion gas canstrike against the pin 26 to have combustion residues adhered to the pin26. In FIG. 11, the pin 26 can be extended until the distal end portion26 a thereof abuts against the opposite wall surface 22 a.

[0303] The gas generator 30 includes an ignition means (an electricaltype igniter) 34 and a gas generating agent 36 accommodated in a gasgenerator housing 32, and it is connected to one end of the pressurizedgas chamber 20. The gas generator housing 32 and the pressurized gaschamber housing 22 are connected at a connecting portion 49 byresistance-welding. When the inflator 10 is assembled in an air bagsystem, the ignition means 34 is connected to an external power sourcevia a connector and a lead wire.

[0304] The gas generating agent 36 can comprises, for example, 34 mass %of nitroguanidine as a fuel, 56 mass % of strontium nitrate as anoxidizing agent, and 10 mass % of sodium carboxymethylcellulose as abonding agent (a discharged gas temperature: 700 to 1630° C.). Acombustion residue generated when the gas generating agent 36 of theabove composition is burnt is strontium oxide (melting point: 2430° C.).For this reason, the combustion residue is solidified to be massive(slag-like) without being melted.

[0305] A first communication hole 38 between the pressurized gas chamber20 and the gas generator 30 is closed by a first rupturable plate 40 ina bowl-like shape, and the interior of the gas generator 30 ismaintained in the normal pressure. The first rupturable plate 40 isresistance-welded to the gas generator housing 32 at a peripheral edgeportion 40 a.

[0306] A cap 44 having gas ejecting holes 42 is covered over the firstrupturable plate 40 from the pressurized gas chamber 20 side. The cap 44is attached to cover the first rupturable plate 40, so that combustiongas generated by combustion of the gas generating agent 36 is alwaysejected from the gas ejecting holes 42 via the cap 44.

[0307] A distance L1 between a closed end surface 44 b of the cap 44 andan gas ejecting hole 42 nearest to the closed end surface 44 b and adiameter D1 of the rupturable plate 40 (except for a welded peripheraledge portion) satisfy the following formula: L1≧D1/2.

[0308] The distance L1 is preferably 3 to 8 mm, more preferably 4 to 8mm, and particularly preferably 5 to 8 mm. The diameter of a pluralityof the gas ejecting holes 42 is preferably 0.5 to 2 mm, and morepreferably 0.5 to 1.2 mm. The total opening area of a plurality of thegas ejecting holes 42 is preferably 20 to 1000 mm², and more preferably100 to 500 mm².

[0309] The cap 44 has a flange portion 46 formed by folding an openingperipheral edge portion outwardly, and it is fixed by crimping a portion(a crimping portion) 48 of the gas generator housing 32 at the flangeportion 46.

[0310] A diffuser portion 50 having gas discharging holes 52 fordischarging the pressurized gas and the, combustion gas is connected tothe other end side of the pressurized gas chamber 20, and the diffuserportion 50 and the pressurized gas chamber housing 22 isresistance-welded to each other at a connecting portion 54.

[0311] The diffuser portion 50 is a cap-shaped one having a plurality ofgas discharging ports 52 through which a gas passes, wherein a distanceL2 between a closed end surface 51 and an gas discharging port nearestto the closed end surface 51 and a diameter D2 of the rupturable plate58 (except for a welded peripheral edge portion) satisfy the followingformula: L2 ≧D2/2.

[0312] The distance L2 is preferably 3 to 8 mm, more preferably 4 to 8mm, and particularly preferably 5 to 8 mm. The diameter of a pluralityof the gas discharging ports 52 is preferably 0.5 to 2 mm, and morepreferably 0.5 to 1.2 mm. The total opening area of a plurality of thegas discharging ports 52 is preferably 20 to 1000 mm², and morepreferably 100 to 500 mm².

[0313] A second communication hole 56 between the pressurized gaschamber 20 and the diffuser portion 50 is closed by a second rupturableplate 58, and the interior of the diffuser portion 50 is maintained inthe normal pressure. The second rupturable plate 58 is resistance-weldedto the diffuser portion 50 at a peripheral edge portion 58 a.

[0314] Next, an operation in case of the inflator 10 shown in FIG. 13which is incorporated to an air bag system mounted to an automobile willbe explained.

[0315] When an automobile receives the impact by a collision, theigniter 34 is actuated and ignited by the activation-signal outputtingmeans to burn the gas generating agent 36, thereby generating a hightemperature combustion gas. At this time, since the melting point of acombustion residue generated by combustion of the gas generating agent36 is equal to or more than a discharging temperature of a gas generatedfrom the gas generating agent 36, the combustion residue can hardlymelt, being maintained solid.

[0316] Thereafter, the first rupturable plate 40 is broken by a pressurerise inside the gas generator 30 due to the high temperature combustiongas, and combustion gas including a combustion residue flows into thecap 44 to be ejected from the gas ejecting holes 42.

[0317] At this time, the pressurized gas flows out from the gas ejectingholes 42 after the pressurized gas strikes against the closed endsurface 44 b of the cap 44 to change its flow direction, so that foreignmaterials can easily remain at a pocket portion from the closed endsurface 44 b to the gas ejecting hole 42 nearest to the closed endsurface 44 b. And, since the above-described action is enhanced bysetting the depth (L1) of the pocket portion to the maximum length(D1/2) of the foreign material or more, the foreign materials can remainmore easily in the pocket. As described above, the gas is dischargedfrom the cap 44 to remove the foreign materials.

[0318] Further, since a temperature difference between the pressurizedgas and the combustion gas in the pressurized gas chamber 20 is large,the combustion gas is cooled rapidly, so that the high temperaturecombustion residue is cooled and solidified and a combustion residuealso adheres to the closed end surface 44 b of the cap 44. Further, theejected combustion gas strikes against an inner wall 22 a of thepressurized gas chamber housing 22, so that the combustion residueadheres to an inner wall surface and it can be hardly discharged out ofthe inflator 10. Incidentally, part of the remaining combustion residueadheres to the pin 26, too.

[0319] Thereafter, the second rupturable plate 58 is broken by apressure rise inside the pressurized gas chamber 20, and consequently,the pressurized gas and the combustion gas are discharged from the gasdischarging holes 52 via the second communication hole 56 to inflate anairbag. At this time, since the relationship of L2≧D2/2 is satisfiedeven in the diffuser portion 50, an action similar to that of the cap 44can be conducted.

[0320] In such a course of action, the inflator 10 exhibits theabove-described advantageous effects (IIa) to (IIc), (1) to (3) anamount of pieces of the rupturable plate or combustion residuesdischarged in the air bag is largely suppressed. In an actualmeasurement, when the cap 44 was not provided in the structure shown inFIG. 13 and the relationship of L2≧D2/2 was not satisfied in thediffuser portion 50, combustion residues discharged outside the inflator10 was 700 mg. However, it was reduced to 200 mg by employing thestructure shown in FIG. 13.

[0321] (4) Embodiment 4

[0322] One embodiment will be explained with reference to FIG. 14. FIG.14 is a sectional view of an inflator in the axial direction. Since theinflators shown in FIG. 14 and FIG. 13 have the same structure exceptthat the inflator shown in FIG. 14 is further provided with a capcovering the second rupturable plate, so that the same elements areattached with the same reference numerals and explanations thereof willbe omitted.

[0323] A cap 64 having a gas outflow holes 62 covers a second rupturableplate 58 from the pressurized gas chamber 20 side. The cap 64 isattached to cover the second rupturable plate 58 so that combustion gasgenerated by combustion of a gas generating agent 36 always passes thecap 64 and flows into a diffuser portion 50 from the gas outflow holes62. Reference numeral 62 denotes the gas outflow hole, reference numeral68 denotes a flange portion, and the cap 64 is fixed to the diffuserportion 50 by the flange portion 68 and crimping portion 59. Thediameter of and the total opening area of a plurality of the gas outflowholes 62 can be made equal to those in the gas ejecting holes 42.

[0324] In the inflator 10 shown in FIG. 14, the cap 44 and the diffuserportion 50 satisfy the relation of L1≧D1/2 and the relation of L2≧D2/2like the inflator 10 shown in FIG. 13 and the cap 64 is furtherprovided, so that the advantageous effects (IIa) to (IIc) are furtherenhanced.

[0325] (5) Embodiment 5

[0326] Another embodiment will be explained with reference to FIG. 15.FIG. 15 is a sectional view of an inflator in the axial direction. Aninflator 100 shown in FIG. 15 has almost the same structure as that ofthe inflator 10 shown in FIG. 13, and the same reference numerals asthose in FIG. 13 denote the same parts in FIG. 15. A difference instructure from FIG. 13 and an advantageous effect due to the differencein structure will be explained below.

[0327] In the inflator 100 shown in FIG. 15, an inner wall surface 22 aof a pressurized gas chamber housing 22 has a groove with a depth of 0.2mm formed continuously or discontinuously in the circumferentialdirection. For this reason, combustion residues in combustion gas isarrested in the groove, and thereby, an advantageous effect (4) can beexhibited in addition to the advantageous effects (1) to (3). Further,as shown in FIG. 14, an aspect in which a cap 64 is provided can beemployed.

[0328] Further, the cap 44 and the diffuser portion 50 satisfy therelation of L1≧D1/2 and the relation of L2≧D2/2 like the inflator 10shown in FIG. 13, the advantageous effects (IIa) to (IIc) can beobtained.

[0329] (6) Embodiment 6

[0330] Another embodiment will be explained with reference to FIG. 16.FIG. 16 is a sectional view of an inflator in the axial direction. Aninflator 200 shown in FIG. 16 has almost the same structure as that ofthe inflator 10 shown in FIG. 13, and, in FIG. 16, the same referencenumerals as those in FIG. 13 denote the same parts. A difference instructure from FIG. 13 and an advantageous effect due to the differencein structure will be explained below.

[0331] In the inflator 200 shown in FIG. 16, gas ejecting holes 42 areprovided on a side surface of a cap 44 and they are opened to ejectcombustion gas towards the gas generator 30. For this reason, thecombustion gas ejected from the gas ejecting holes 42 strikes against acrimped portion 48 and its vicinities before it strikes against theinner wall surface 22 a of the pressurized gas chamber housing 22, andthereby, an advantageous effect (5) can be exhibited in addition to theadvantageous effects (1) to (3). Incidentally, when the aspect shown inFIG. 15 is employed with respect to the inner wall surface 22 a of thepressurized gas chamber housing 22, the advantageous effect (4) can befurther exhibited. Also, as shown in FIG. 14, the aspect in which thecap 64 is provided can be employed, and the cap 44 of another embodimentcan be used instead of the cap 64.

[0332] Further, since the cap 44 and the diffuser portion 50 satisfy therelation of L1≧D1/2 and the relation of L2≧D2/2 like the inflator 10shown in FIG. 13, the advantageous effects (IIa) to (IIc) can beobtained.

[0333] (7) Embodiment 7

[0334] Another embodiment will be explained with reference to FIG. 5 toFIG. 7. FIG. 5 is a perspective view and a plan view of a cap of oneembodiment, FIG. 6 is a perspective view and a plan view of a cap ofanother embodiment, and FIG. 7 is a perspective view of a cap of anotherembodiment. A cap 44 shown in FIG. 5 to FIG. 7 can be disposed into theinflators 600, 700, 10, 100 and 200 shown in FIG. 11 to FIG. 16respectively.

[0335] In the cap 44 shown in FIG. 5, gas ejecting holes 42 are providedon a side surface of the cap 44 a, and a member (restricting member) 45for circumferentially restricting an ejecting direction of combustiongas from the gas ejecting holes 42. The restricting member 45 is formedin a L-letter shape in plan view. Incidentally, the orientation of therestricting member 45 may be a different direction from that in FIG. 5.

[0336] Since such restricting members 45 are provided, combustion gasejected from the gas ejecting hole 42 is ejected in the direction alongthe circumferential surface of the cap 44 to form an eddy, so that theadvantageous effect (5) can be exhibited in addition to the advantageouseffects (1) to (3). Incidentally, when the shape shown in FIG. 15 can beemployed for the inner wall surface 22 a of the pressurized gas chamberhousing 22, the advantageous effect (4) can be further exhibited.

[0337] The cap 44 shown in FIG. 7 is provided with flat plate-shapedrestricting members 45 instead of the L-letter-shaped restrictingmembers 45 shown in FIG. 5, and the same advantageous effect as those inFIG. 5 can be obtained.

[0338] The cap 44 shown in FIG. 7 is provided on its end surface 44 awith gas ejecting holes 42, and members (restricting members) 45 forcircumferentially restricting an ejected direction of combustion gasfrom the gas ejecting holes 42. The restricting member 45 can be formedin the same shape as shown in FIG. 5 or FIG. 6. An inflator using thecap 44 shown in FIG. 7 can obtain the same advantageous effects as thosein FIG. 5 and FIG. 6.

[0339] By adjusting the caps 44 shown in FIG. 5 and FIG. 6 to satisfythe relation of L1≧D1/2, the advantageous effects (IIa) to (IIc) can beobtained like the inflator 10 shown in FIG. 13. In particular, when thecaps 44 shown in FIG. 5 and FIG. 6 are used, pieces of the broken firstrupturable plate 40 can hardly be discharged out through the gasejecting holes 42 due to an action of the restricting members, andthereby an arresting effect is further improved.

[0340] (8) Embodiment 8

[0341] Another embodiment will be explained with reference to FIG. 10.FIG. 10 is a sectional view of an inflator in the axial direction. Aninflator 300 shown in FIG. 10 has almost the same structure as that ofthe inflator 10 shown in FIG. 13, and, in FIG. 10, the same referencenumerals as these in FIG. 13 denote the same parts. A difference instructure from FIG. 13 and a difference in advantageous effect due tothe difference in structure will be explained below.

[0342] In the inflator 300 shown in FIG. 10, a cylindrical barriermember 310 is attached thereto. The barrier member 310 has a closed oneend integrated with a end surface of the cap 44 b and the other endopened, and it is formed such that a side wall 311 faces gas ejectingholes 42 provided on the side surface of the cap 44 a with a distance.Also, as shown in FIG. 14, the aspect in which the cap 64 is providedcan be employed, and further, the cap 44 of the other embodiment can beemployed instead of the cap 64.

[0343] Since the cap 44 and the diffuser portion 50 satisfy the relationof L1≧D1/2 and the relation of L2≧D2/2 like the inflator 10 shown inFIG. 13, the advantageous effects (IIa) to (IIc) can be obtained.

[0344] Further, because of a barrier member 310 provided with the cap44, the combustion gas ejected from the gas ejecting holes 42 strikesagainst an inner wall of a side wall 311 of the barrier member, andthen, it moves from the opening. Thereby, the advantageous effect (6)can be exhibited in addition to the advantageous effects (1) to (3).Incidentally, when the aspect shown in FIG. 15 is employed with respectto the inner wall surface 22 a of the pressurized gas chamber housing22, the advantageous effect (4) can be exhibited as well.

[0345] (9) Embodiment 9

[0346] Another embodiment will be explained with reference to FIG. 11.FIG. 11 is a sectional view of an inflator in the axial direction. Aninflator 400 shown in FIG. 11 has almost the same structure as that ofthe inflator 10 shown in FIG. 13, and, in FIG. 11, the same referencenumerals as those in FIG. 13 denote the same parts. A difference instructure from FIG. 13 and a difference in advantageous effect due tothe difference in structure will be explained below.

[0347] In the inflator 400 shown in FIG. 11, a disk-like barrier member410 is attached. The barrier member 410 is integrated with a end surfaceof the cap 44 b and it is extended from the end surface of the cap 44 btowards an inner wall surface 22 a of the pressurized gas chamberhousing 22. Also, as shown in FIG. 14, the aspect in which the cap 64 isprovided can be employed, and further, the cap 44 of another embodimentcan be used instead of the cap 64.

[0348] Since the cap 44 and the diffuser portion 50 satisfy the relationof L1≧D1/2 and the relation of L2≧D2/2 like the inflator 10 shown inFIG. 13, the advantageous effects (IIa) to (IIc) can be obtained.

[0349] Further, because of a barrier member 410 attached to the cap 44,combustion gas ejected from the gas ejecting holes 42 strikes againstthe barrier member 410, and then, it moves from a clearance between theinner wall surface 22 a of the pressurized gas chamber housing 20 and anperipheral edge portion 411 of the barrier member. Thereby, theadvantageous effect (6) can be exhibited in addition to the advantageouseffects (1) to (3). Incidentally, when the aspect shown in FIG. 15 isemployed with respect to the inner wall surface 22 a of the pressurizedgas chamber housing 22, the advantageous effect (4) can further beexhibited.

[0350] (10) Embodiment 10

[0351] Another embodiment will be explained with reference to FIG. 12.FIG. 12 is a sectional view of an inflator in the axial direction. Aninflator 500 shown in FIG. 12 has almost the same structure as that ofthe inflator 10 shown in FIG. 13, and, in FIG. 12, the same referencenumerals as those in FIG. 13 denote the same parts. A difference instructure in FIG. 13 and a difference in advantageous effect due to thedifference in structure will be explained below.

[0352] In the inflator 500 shown in FIG. 12, a disk-like barrier member510 is attached. The barrier member 510 is integrated with an endsurface of the cap 44 b, and it is extended from the end surface of thecap 44 b towards the inner wall surface 22 a of the pressurized gaschamber housing 20 so that a peripheral edge portion 511 abuts on theinner wall surface 22 a. Gas passing ports 512 and restricting means 513having similar shapes like those in FIG. 8 are provided in theperipheral edge portion 511. Also, as shown in FIG. 14, the aspect inwhich the cap 64 is provided can be employed and further, the cap 44 ofanother embodiment can be used instead of the cap 64.

[0353] Since the cap 44 and the diffuser portion 50 satisfy the relationof L1≧D1/2 and the relation of L2≧D2/2 like the inflator 10 shown inFIG. 13, the advantageous effects (IIa) to (IIc) can be obtained.

[0354] Further, because of a barrier member 510 attached to the cap 44,combustion gas ejected from the gas ejecting holes 42 strikes againstthe barrier member 510, and then, it moves through the gas passing ports512 and the restricting means 513. Thereby, the advantageous effects (6)and (5) can be exhibited in addition to the advantageous effects (1) to(3). Incidentally, when the aspect shown in FIG. 14 is employed withrespect to the inner wall surface 22 a of the pressurized gas chamberhousing 22, the advantageous effect (4) can further be exhibited.

[0355] The inflator of the present invention can be applied to variousinflators such as an air bag inflator for a driver side, an air baginflator for a passenger side next to a driver, an air bag inflator fora side collision, an inflator for a curtain air bag, an inflator for aknee-bolster, an inflator for an inflatable seat belt, an inflator for atubular system, an iflator for a pretensioner and the like.

[0356] Embodiments of the Invention (III)

[0357] Inflators of the present invention will be explained withreference to FIG. 20 and FIG. 21. FIG. 20 and FIG. 21 are crosssectional views of embodiments of the present invention. An inflator 10shown in FIG. 20 and an inflator 100 shown in FIG. 21 have almost thesame structure except that the axial size of the inflator 10 is shorterthan that of the inflator 100 and these inflators are different fromeach other in structure of a diffuser portion.

[0358] The inflator 10 comprises a pressurized gas chamber 20, a gasgenerator 30 and a diffuser 50, and outer diameters of these members areset to approximately the same.

[0359] The pressurized gas chamber 20 has an outer shell formed by acylindrical pressurized gas chamber housing 22 and it is charged withpressurized gas comprising a mixture of argon and helium, not includingoxygen gas.

[0360] The pressurized gas chamber housing 22 is symmetrical axially andradially, and outer diameters at both ends are reduced to about 22 mmrelative to an outer diameter D (about 25 mm) at the central portionthereof. Since a length L of the pressurized gas housing 22 is set toabout 50 to 250 mm, L/D is 1 to 10.

[0361] Since the pressurized gas chamber housing 22 has such a shape, itis unnecessary to adjust the orientation of the pressurized gas chamberhousing in the axial and radial directions at a time of assembling, andjoining work of the gas generator 30 and the diffuser portion 50effected by resistance-welding or the like can be facilitated.

[0362] A charging hole 24 for pressurized gas is formed on a sidesurface of the pressurized gas chamber housing 22, and it is closed by apin 26 after pressurized gas is charged. A distal end portion 26 a ofthe pin 26 protrudes into the pressurized medium chamber 20, and theprotruding portion thereof has such a length that combustion gas flow ofa gas generating agent strikes against the protruding portion. Byadjusting the length of the protruding portion of the pin 26, combustiongas can strike against the pin 26 to have combustion residues adhered tothe pin 26. In FIG. 20, the pin 26 can be extended until the distal endportion 26 a thereof abuts against the opposite wall surface 22 a.

[0363] The gas generator 30 includes an ignition means (an electricaltype igniter) 34 and a gas generating agent 36 accommodated in a gasgenerator housing 32, and it is connected to one end of the pressurizedgas chamber 20. The inflator 10 is fixed by crimping the part 35 of thegas generator housing 35.

[0364] The gas generator housing 32 and the pressurized gas chamberhousing 22 are connected at a connecting portion 49 byresistance-welding. When the inflator 10 is assembled in an air bagsystem, the ignition means 34 is connected to an external power sourcevia a connector and a lead wire.

[0365] A first communication hole 38 between the pressurized gas chamber20 and the gas generator 30 is closed by a first rupturable plate 40transformed into a bowl-like shape due to a pressure of the pressurizedgas, and the interior of the gas generator 30 is maintained in thenormal pressure. The first rupturable plate 40 is resistance-welded tothe gas generator housing 32 at a peripheral edge portion 40 a.

[0366] A cap 44 having gas ejecting holes 42 is covered over the firstrupturable plate 40 from the pressurized gas chamber 20 side. The cap 44is attached to cover the first rupturable plate 40, so that combustiongas generated by combustion of the gas generating agent 36 is alwaysejected from the gas ejecting holes 42 via the cap 44.

[0367] The cap 44 has a flange portion 46 formed by folding an openingperipheral edge portion outwardly, and it is fixed by crimping a portion(a crimping portion) 48 of the gas generator housing 32 at the flangeportion 46.

[0368] A diffuser portion 50 having gas discharging holes 52 fordischarging the pressurized gas and the combustion gas is connected tothe other end side of the pressurized gas chamber 20, and the diffuserportion 50 and the pressurized gas chamber housing 22 isresistance-welded to each other at a connecting portion 54. A filtermade of wire mesh can be disposed inside the diffuser portion 50 inorder to arrest the combustion residue, if required.

[0369] A second communication hole 56 between the pressurized gaschamber 20 and the diffuser portion 50 is closed by a second rupturableplate 58 transformed into a bowl-like shape due to pressure of thepressurized gas, and the interior of the diffuser portion 50 ismaintained in the normal pressure. The second rupturable plate 58 isresistance-welded to the diffuser portion 50 at a peripheral edgeportion 58 a.

[0370] The detail of requirements (1) to (8) in an inflator 10 shown inFIG. 20 is as follows:

[0371] Requirements (1) and (6)

[0372] Pressurized gas comprising a mixture of argon and helium, but notincluding oxygen gas is charged in a gas generator 20 under a chargingpressure of 30,000 to 67,000 kPa.

[0373] Requirements (2) and (5)

[0374] As a gas generating agent 36, one with a cylindrical shapecomprising nitroguanidine/strontium nitrate/sodiumcarboxymethylcellulose/acid clay=34.3/49.6/9.4/6.7 (mass %) (pressureindex 0.6, combustion flame temperature=2098° C.) is used in the amountof 1.9 to 5.3 g.

[0375] Requirement (3)

[0376] A ratio of an amount (mole number) of pressurized gas (Al) and anamount (mole number) of a gas generated by combustion of a gasgenerating agent (A2), A1/A2=1 to 20;

[0377] Requirement (4)

[0378] A ratio of a mass of pressurized gas (B1) and a mass of a gasgenerating agent (B2), B1/B2=1 to 20;

[0379] Requirement (7)

[0380] A ratio of an amount (mole number) of pressurized gas (A1) and atotal surface opening (cm²) of a gas generating agent (C) A1/C=0.004 to0.05 mole/cm²;

[0381] Requirement (8)

[0382] A ratio of a total surface area (cm²) of a gas generating agent(C) and a total area (cm²) of gas discharging holes (D), C/D is 0.5 to4;

[0383] Next, an operation of the inflator 10 shown in FIG. 20 which isassembled in an air bag system mounted on an automobile will beexplained.

[0384] When an automobile receives the impact by collision, the igniter34 is activated and ignited upon receiving an actuation signal from acontrol unit to burn the gas generating agent 36, and thereby,combustion gas with a high temperature is generated.

[0385] Thereafter, the first rupturable plate 40 is broken by a pressurerise inside the gas generator 30 due to the high temperature combustiongas, and combustion gas including a combustion residue flows into thecap 44 to be ejected from the gas ejecting holes 42. At this time, sincea temperature difference between the pressurized gas and the combustiongas in the pressurized gas chamber 20 is large, the combustion gas iscooled rapidly, so that the high temperature combustion residue iscooled and solidified and a combustion residue also adheres to an innerwall surface of an end surface 44 a of the cap 44. Further, since thecombustion gas ejected strikes against an inner wall 22 a of thepressurized gas chamber housing 22, the combustion residue adheres to aninner wall surface and it can be hardly discharged out of the inflator10. Incidentally, part of the remaining combustion residue adheres tothe pin 26, too.

[0386] Thereafter, since the second rupturable plate 58 is broken by apressure rise inside the pressurized gas chamber 20, the pressurized gasand the combustion gas are discharged from the gas discharging holes 52via the second communication hole 56 to inflate an air bag.

[0387] In such a course of action, since the inflator 10 is providedwith the above-described requirements (1) to (6), or preferably (1) to(8), the internal pressure in the inflator is controlled not to riseexcessively when the gas generating agent is burnt, even with the highpressurized-gas charging pressure of 30,000 to 67,000 kPa. As a result,the air bag can be inflated within an optimal time for protecting anoccupant (generally, which is considered to be 10 to 30 msec).

[0388] Further, an internal pressure of the inflator when the gasgenerating agent is burnt can be controlled suitably, and thereby, thesize of the inflator can be made small to downsize of the inflator whilethe charged amount of the pressurized gas is maintained to be equal tothat in the prior art, that is, an amount of the pressurized gas forinflating the air bag is secured. And, as the result of downsizing theinflator, even when the charging pressure of the pressurized gas rises,an internal pressure of the inflator at an actuation can be controlledsuitably.

[0389] The inflators of the present invention can be applied to variousinflators such as an air bag inflator for a driver side, an air baginflator for a passenger side next to a driver, an air bag inflator fora side collision, an inflator for a curtain air bag, an inflator for aknee-bolster, an inflator for an inflatable seat belt, an inflator for atubular system, an inflator for a pretensioner and the like.

EXAMPLES

[0390] The present invention will be explained in detail as follows onthe basis of Examples, but the present invention is not limited to theseExamples.

Example 1

[0391] An inflator having the structure shown in FIG. 20 was produced.An entire length of the inflator was 110 mm, a length (L) of apressurized gas chamber housing is 60 mm, an outer diameter (D) thereofis 25 mm, an thickness thereof is 2 mm (material: seamless steel pipe),and outer diameters of the other portions of the inflator were almostthe same. The detail of the requirements (1) to (8) and the like are asfollows:

[0392] Requirement (1): A mixed gas comprising 96 mole % of argon and 4mole % of helium but not including oxygen gas;

[0393] Requirement (2): one in a cylindrical shape comprisingnitroguanidine/strontium nitrate/sodium carboxymethylcellulose/acidclay=34.3/49.6/9.4/6.7 (mass %) (pressure index=0.6, combustion flametemperature=2098° C.)

[0394] Requirement (3): A1/A2=0.3/0.047=6.4;

[0395] Requirement (4): B1/B2=11.7/1.9=6.2;

[0396] Requirement (5): The amount of a gas generating agent was 1.9

[0397] Requirement (6): The charging pressure of pressurized gas was42,000 kPa;

[0398] Requirement (7): A1/C=0.3/46.9=0.0064;

[0399] Requirement (8): C/E=46.9/21.2=2.2; L/D=2.4;

[0400] A well known 60 L tank combustion test, for example, as describedin a paragraph 11 of JP-B No. 2963086, was conducted with this inflator.A tank curve is shown in FIG. 22.

[0401] As apparent from the tank curve shown in FIG. 22, even when theinflator itself was downsized and an internal pressure of the inflatorwas high before actuation, an internal pressure of the inflator at anactuation time was controlled by satisfying the requirements (1) to (8).As a result, it was confirmed that the air bag was inflated maximally atabout 10 msec and that the inflator was normally actuated.

Example 2

[0402] An inflator having the structure shown in FIG. 21 was produced.An entire length of the inflator was 280 mm, a length (L) of apressurized gas chamber housing is 200 mm, an outer diameter (D) thereofis 25 mm, an thickness thereof is 2 mm (material: seamless steel pipe),and outer diameters of the other portions of the inflator were almostthe same. The detail of the requirements (1) to (8) and the like are asfollows:

[0403] Requirement (1): A mixed gas comprising 96 mole % of argon and 4mole % of helium but not including oxygen gas;

[0404] Requirement (2): one in a cylindrical shape comprisingnitroguanidine/strontium nitrate/sodium carboxymethylcellulose/acidclay=34.3/49.6/9.4/6.7 (mass %) (pressure index=0.6, combustion flametemperature=2098° C.)

[0405] Requirement (3): A1/A2=1.09/0.130=8.4;

[0406] Requirement (4): B1/B2=42/5.3=7.9;

[0407] Requirement (5): The amount of a gas generating agent was 5.3 g;

[0408] Requirement (6): The charging pressure of pressurized gas was42,000 kPa;

[0409] Requirement (7): A1/C=1.09/72.5=0.015;

[0410] Requirement (8): C/E=72.5/42.4=1.7; L/D=8.0;

[0411] The same 60-liter tank combustion test was conducted with thisinflator as in Example 1, and a tank curve generally equal to that inFIG. 22 was obtained.

[0412] Incidentally, when compared with the fact that, in the paragraph136 of in JP-A 9-76870 described as the prior art, there is adescription that an interior of an inflator housing is maintained in ahigh pressure such as 4000 psi (27,600 kPa) or so, an internal pressureof the inflator of Example 1 at a time of actuation is expected to bemuch higher than that in the prior art. However, since the requirements(1) to (8) were provided, an internal pressure of the inflator wascontrolled so that the inflator was normally operated.

1. An inflator inflating an air bag with combustion gas generated bycombustion of a gas generating agent and a pressurized medium, andcomprising a means for making the combustion gas strike against one orat least two wall surfaces to have combustion residues in the combustiongas adhered to the one or at least two wall surfaces and a means formaking the combustion gas contact with the pressurized medium to cooland solidify the combustion residues contained in the combustion gas dueto a temperature difference, wherein a melting point of the combustionresidues produced by combustion of the gas generating agent is not lessthan a discharging temperature of gas generated from the gas generatingagent.
 2. An inflator inflating an air bag with combustion gas generatedby combustion of a gas generating agent and a pressurized medium, andcomprising a means for changing a flowing direction of the combustiongas to have combustion residues in the combustion gas adhered to one orat least two wall surfaces and a means for making the combustion gascontact with the pressurized medium to cool and solidify the combustionresidues contained in combustion gas due to a temperature difference,wherein a melting point of the combustion residues produced bycombustion of the gas generating agent is not less than a dischargingtemperature of gas generated from the gas generating agent.
 3. Aninflator according to claim 1 or 2, comprising a pressurized mediumchamber having an outer shell formed with a cylindrical pressurizedmedium chamber housing and charged with a pressurized medium, a gasgenerator connected to one end of the pressurized medium chamber andincluding an ignition means and a gas generating agent accommodated in agas generator housing, and a diffuser portion which is connected to theother end of the pressurized medium chamber, wherein a first rupturableplate closes between the pressurized medium chamber and the gasgenerator, a second rupturable plate closes between the pressurizedmedium chamber and the diffuser portion, and further a cap having a gasejecting hole provided on at least one of a side surface and an endsurface thereof covers the first rupturable plate from the pressurizedmedium chamber side.
 4. An inflator comprising a pressurized mediumchamber having an outer shell formed with a cylindrical pressurizedmedium chamber housing and charged with a pressurized medium, a gasgenerator connected to one end of the pressurized medium chamber andincluding an ignition means and a gas generating agent accommodated in agas generator housing, and a diffuser portion which is connected to theother end of the pressurized medium chamber, wherein a first rupturableplate closes between the pressurized medium chamber and the gasgenerator, a second rupturable plate closes between the pressurizedmedium chamber and the diffuser portion, a cap having a gas ejectinghole covers the first rupturable plate from the pressurized mediumchamber side and further, at least one selected from the followingrequirements (a), (b) and (c) is provided: (a) an inner wall surface ofthe pressurized medium chamber housing is rough; (b) the gas ejectinghole is oriented so that combustion gas ejected from the gas ejectinghole does not strike against an inner wall surface of a pressurizedmedium chamber housing by airline distance; and (c) a barrier member isdisposed in the vicinity of the gas ejecting hole, and combustion gasejected from the gas ejecting hole moves after it strikes against thebarrier member.
 5. An inflator according to claim 4, wherein, in therequirement (a), the inner wall surface of the pressurized mediumchamber housing has a groove formed continuously or discontinuously inthe circumferentical direction.
 6. An inflator according to claim 5,wherein a depth of the groove is not less than 0.2 mm.
 7. An inflatoraccording to claim 4, wherein, in the requirement (b), the gas ejectinghole is provided on a side surface of the cap and is opened towards thegas generator.
 8. An inflator according to claim 4, wherein, in therequirement (b), the gas ejecting hole is provided on an side surface ofthe cap, and a member for circumferentially restricting an ejectingdirection of combustion gas from the gas ejecting hole is provided. 9.An inflator according to claim 4, wherein, in the requirement (b), thegas ejecting hole is provided on an end surface of the cap, and a memberfor circumferentially restricting an ejecting direction of combustiongas from the gas ejecting hole is provided.
 10. An inflator according toclaim 4, wherein, in the requirement (c), the barrier member iscylindrical one end side thereof is closed integrally with the endsurface of the cap, the other end thereof is opened and a side surfacethereof is formed to face the gas ejecting hole provided in the sidesurface of the cap with a gap, and combustion gas moves from the openingafter it strikes against a side surface inner wall of the cylindricalmember.
 11. An inflator according to claim 4, wherein, in therequirement (c), the barrier member is disk-shaped, integrated with theend surface of the cap and extended from the end surface of the captowards an inner wall surface of the pressurized medium chamber housing,and after combustion gas ejected from the gas ejecting hole provided inthe side surface of the cap strikes against a peripheral edge portion ofthe barrier member, the combustion gas moves from a gap between theinner wall surface of the pressurized medium chamber housing and theperipheral edge portion of the barrier member.
 12. An inflator accordingto claim 4, wherein, in the requirement (c), the barrier member isdisk-shaped, integrated with the end surface of the cap and extendedfrom the end surface of the cap towards an inner wall surface of thepressurized medium chamber housing so that a peripheral edge portionthereof abuts on the inner wall surface, a gas passing port is providedin the peripheral edge portion of the barrier member and a member forcircumferentially restricting an ejecting direction of gas from the gaspassing port is provided, and combustion gas ejected from the gasejecting hole provided in the side surface of the cap is ejected fromthe gas passing port.
 13. An inflator according to claim 4, which isprovided with the requirements (a) and (b), the requirements (a) and (c)the requirements (b) and (c), or the requirements (a), (b) and (c). 14.An inflator according to claim 3 or 4, wherein the cap has a flangeportion formed by outwardly folding a peripheral edge portion of theopening and is fixed at the flange portion by crimping part of the gasgenerator housing.
 15. An inflator according to claim 3 or 4, whereinthe housing forming the pressurized medium chamber is symmetricalregarding the axial and radial directions.
 16. An inflator according toclaim 3 or 4, wherein a pressurized medium charging hole is formed in aside surface of the pressurized medium chamber housing, and the charginghole is closed by a pin after the pressurized medium is charged.
 17. Aninflator according to claim 16, wherein the pin protrudes into thepressurized medium chamber and the protruding portion thereof has such alength that combustion gas flow of the gas generating agent strikesagainst the protruding portion.
 18. An inflator according to claim 3 or4, wherein the as generator housing and the pressurized medium chamberhousing are connected to each other by resistance-welding.
 19. Aninflator according to claim 4, wherein, in the gas generating agent, amelting point of combustion residues produced by combustion of the gasgenerating agent is not less than a discharging temperature of a gasgenerated from the gas generating agent.
 20. An inflator according toany one of claims 1, 2 and 4, wherein the gas generating agent includes20 to 60 mass % of nitroguanidine and 80 to 40 mass % of an oxdizingagent.
 21. An inflator according to any one of claims 1, 2 and 4,wherein the pressurized medium comprises argon and helium.
 22. Aninflator according to any one of claims 1, 2 and 4, wherein a ratio(A/B) of mole number (A) of the pressurized medium and a mole number (B)of a gas generated by combustion of the gas generating agent is 0.2 to10.
 23. An inflator inflating an air bag with combustion gas generatedby combustion of a gas generating agent and a pressurized medium, andcomprising a pressurized gas chamber having an outer shell formed with acylindrical pressurized gas chamber housing and charged with apressurized gas, a gas generator connected to the pressurized gaschamber and including an ignition means and a gas generating agentaccommodated in a gas generator housing, and a diffuser portionconnected to a portion other than the pressurized gas chamber, wherein afirst rupturable plate closes between the pressurized gas chamber andthe gas generator, a second rupturable plate closes between thepressurized gas chamber and the diffuser portion, wherein the diffuserportion is a cap having a plurality of gas discharging holes throughwhich gas passes and at least one of pieces generated by breaking thefirst and the second rupturable plates and a residues contained incombustion gas produced by combustion of the gas generating agent isprevented from flowing outside the inflator.
 24. An inflator accordingto claim 23, wherein a cap which has a plurality of gas dischargingholes through which gas passes and prevents at least one of piecesgenerated by breaking the first rupturable plate and combustion residuesof the gas generating agent from flowing outside the inflator isdisposed inside the pressurized gas chamber to cover the firstrupturable plate from the pressurized gas chamber.
 25. An inflatoraccording to claim 23 or 24, wherein a cap which has a plurality of gasdischarging holes through which gas passes and prevents at least one ofpieces generated by breaking the first rupturable plate and combustionresidues of the gas generating agent from flowing outside the inflatoris disposed inside the pressurized gas chamber to cover the secondrupturable plate from the pressurized gas chamber.
 26. An inflatoraccording to claim 23 or 24, wherein the cap comprises a cylindricalmember having one end opened and the other end closed, and has aplurality of gas discharging holes on at least a peripheral surfacethereof.
 27. An inflator according to claim 23 or 24, wherein, in thecap, that the relationship between a distance L from a closed endsurface of the cap to a gas discharging hole nearest to the closed endsurface and a diameter D of the rupturable plate satisfies the followingformula: L≧D/2.
 28. An inflator according to claim 27, wherein thedistance L is 3 to 8 mm.
 29. An inflator according to claim 23 or 24,wherein diameters of a plurality of the gas discharging holes in the capare 0.5 to 2 mm.
 30. An inflator according to claim 23 or 24, wherein atotal opening area of a plurality of the gas discharging holes in thecap is 20 to 1000 mm².
 31. An inflator according to claim 23 or 24,wherein the cap is disposed such that the axial direction of the cap andthe axial direction of the pressurized gas chamber housing coincide witheach other.
 32. An inflator according to claim 23 or 24, comprising ameans for changing the flow direction of the combustion gas by the cap,making combustion residues included in the combustion gas adhere to oneor at least two portions of the wall surface, further making thecombustion gas contact with the pressurized gas to cool and solidify thecombustion residues contained in the combustion gas due to a temperaturedifference, wherein a melting point of the combustion residues produceddue to combustion of the gas generating agent is not less than adischarging temperature of a gas generated from the gas generatingagent.
 33. An inflator according to claim 24, further provided with atlease one selected from the following requirements (a) to (c): (a) aninner wall surface of the pressurized gas chamber housing is rough; (b)the gas ejecting hole in the cap is oriented so that combustion gasejected from the gas ejecting hole does not strike against an inner wallsurface of a pressurized gas chamber housing by airline distance; and(c) a barrier member is disposed in the vicinity of the gas ejectinghole, and combustion gas ejected from the gas ejecting hole moves afterit strikes against the barrier member.
 34. An inflator according toclaim 33, wherein, in the requirement (a), the inner wall surface of thepressurized gas chamber housing has a groove formed continuously ordiscontinuously in the circumferentical direction.
 35. An inflatoraccording to claim 33, wherein a depth of the groove is not less than0.2 mm.
 36. An inflator according to claim 33, wherein, in therequirement (b), the gas ejecting hole is provided on a side surface ofthe cap and is opened towards the gas generator.
 37. An inflatoraccording to claim 33, wherein, in the requirement (b), the gas ejectinghole is provided on an side surface of the cap, and a member forcircumferentially restricting an ejecting direction of combustion gasfrom the gas ejecting hole is provided.
 38. An inflator according toclaim 33, wherein, in the requirement (b), the ejecting hole is providedon an end surface of the cap, and a member for circumferentiallyrestricting an ejecting direction of combustion gas from the gasejecting hole is provided.
 39. An inflator according to claim 33,wherein, in the requirement (c), the barrier member is cylindrical, oneend side thereof is closed integrally with the end surface of the cap,the other end thereof is opened and a side surface thereof is formed toface the gas ejecting hole provided in the side surface of the cap witha gap, and combustion gas moves from the opening after it strikesagainst a side surface inner wall of the cylindrical member.
 40. Aninflator according to claim 33, wherein, in the requirement (c), thebarrier member is disk-shaped, integrated with the end surface of thecap and extended from the end surface of the cap towards an inner wallsurface of the pressurized gas chamber housing, and after combustion gasejected from the gas ejecting hole provided in the side surface of thecap strikes against a peripheral edge portion of the barrier member, thecombustion gas moves from a gap between the inner wall surface of thepressurized gas chamber housing and the peripheral edge portion of thebarrier member.
 41. An inflator according to claim 33, wherein, in therequirement (c), the barrier member is disk-shaped, integrated with theend surface of the cap and extended from the end surface of the captowards an inner wall surface of the pressurized gas chamber housing sothat a peripheral edge portion thereof abuts on the inner wall surface,a gas passing port is provided in the peripheral edge portion of thebarrier member and a member for circumferentially restricting anejecting direction of gas from the gas passing port is provided, andcombustion gas ejected from the gas ejecting hole provided in the sidesurface of the cap is ejected from the gas passing port.
 42. An inflatoraccording to claim 33, which is provided with the requirements (a) and(b), the requirements (a) and (c), the requirements (b) and (c), or therequirements (a), (b) and (c).
 43. An inflator according to claim 33 or24, wherein the cap has a flange portion formed by outwardly folding aperipheral edge portion of the opening and is fixed at the flangeportion by crimping part of the gas generator housing.
 44. An inflatoraccording to claim 23 or 24, wherein the housing forming the pressurizedgas chamber is symmetrical regarding the axial and radial directions.45. An inflator according to claim 23 or 24, wherein a pressurized gascharging hole is formed in a side surface of the pressurized gas chamberhousing, and the charging hole is closed by a pin after the pressurizedgas is charged.
 46. An inflator according to claim 45, wherein the pinprotrudes into the pressurized gas chamber and the protruding portionthereof has such a length that combustion gas flow of the gas generatingagent strikes against the protruding portion.
 47. An inflator accordingto claim 23 or 24, wherein the gas generator housing and the pressurizedgas chamber housing are connected to each other by resistance-welding.48. An inflator according to claim 23 or 24, wherein, in the gasgenerating agent, a melting point of combustion residues produced bycombustion of the gas generating agent is not less than a dischargingtemperature of a gas generated from the gas generating agent.
 49. Aninflator according to claim 23 or 24, wherein the gas generating agentincludes 20 to 60 mass % of nitroguanidine and 80 to 40 mass % of anoxidizing agent.
 50. An inflator according to claim 23 or 24, whereinthe pressurized gas comprises argon and helium.
 51. An inflatoraccording to claim 23 or 24, wherein a ratio (A/B) of mole number (A) ofthe pressurized gas and a mole number (B) of a gas generated bycombustion of the gas generating agent is 0.2 to
 10. 52. An inflatorinflating an air bag with pressurized gas and combustion gas generatedby combustion of a gas generating agent, which is provided with thefollowing requirements (1) to (6): (1) pressurized gas contains an inertgas but it does not substantially contain oxygen; (2) in the gasgenerating agent, a pressure index obtained by the following formula:rb=αP^(n) (in the formula, rb: burning velocity, α: coefficient, P:pressure, and n: pressure index) is 0.8 or less; (3) a ratio A1/A2 of anamount (mole number) of pressurized gas (A1) and an amount (mole number)of gas generated by combustion of a gas generating agent (A2) is 1 to20; (4) a ratio B1/B2 of a mass (B1) of pressurized gas (B1) and a mass(B2) of a gas generating agent is 1 to 20; (5) a mass of a gasgenerating agent is 0.5 to 30 g; and (6) a charging pressure ofpressurized gas is 30,000 to 67,000 kPa.
 53. An inflator according toclaim 52, wherein, in the requirement (2), a combustion flametemperature of the gas generating agent is not more than 3000° C.
 54. Aninflator according to claim 52, wherein, in the requirement (2), the gasgenerating agent is a non-azide gas generating agent.
 55. An inflatoraccording to claim 52 or 53, which is further provided with therequirement (7) such that a ratio A1/C of an amount (mole numbers)(A1)of the pressurized gas and a total surface area (cm²) (C) of the gasgenerating agent is 0.004 to 0.05 mole/cm².
 56. An inflator according toclaim 52 or 53, which is further provided with the requirement (8) suchthat a ratio C/E of a total surface area (cm²) (C) of the gas generatingagent and a total area (cm²) (E) of the gas discharging hole is 0.5 to4.
 57. An inflator according to claim 52 or 53, wherein the inflator hasa pressurized gas chamber having an outer shell formed by a cylindricalpressurized gas chamber housing and charged with pressurized gas, and anouter diameter of the pressurized gas chamber housing is preferably notmore than 40 mm.
 58. An inflator according to claim 52 or 53, whereinthe inflator has a pressurized gas chamber having an outer shell formedby a cylindrical pressurized gas chamber housing and charged withpressurized gas, and a ratio (L/D) of an outer diameter (D) and a length(L) of the pressurized gas chamber housing is preferably 1 to
 10. 59. Aninflator according to claim 52 or 53, wherein the inflator has apressurized gas chamber having an outer shell formed by a cylindricalpressurized gas chamber housing and charged with pressurized gas, andthe pressurized gas chamber housing is symmetrical regarding the axialand radial directions.
 60. An inflator according to claim 52 or 53,wherein the inflator has a pressurized gas chamber having an outer shellformed by a cylindrical pressurized gas chamber housing and charged withpressurized gas, and the pressurized gas chamber housing is symmetricalregarding the axial and radial directions and both ends thereof arereduced in diameter.
 61. An inflator according to claim 52 or 53,wherein the inflator has a pressurized gas chamber having an outer shellformed by a cylindrical pressurized gas chamber housing and charged withpressurized gas, a pressurized gas charging hole is formed in a sidesurface of the pressurized gas chamber housing, and the gas charginghole is closed by a pin after the pressurized gas is charged.
 62. Aninflator according to claim 61, wherein the pin is protruding into thepressurized gas chamber housing and a protruding portion thereof hassuch a length that combustion gas flow strikes against the protrudingportion.
 63. An inflator according to claim 52, comprising a pressurizedgas chamber having an outer shell formed by a cylindrical pressurizedgas chamber housing and charged with pressurized gas, a gas generatorhaving an outer shell formed by a gas generator housing and including anignition means and a gas generating agent inside the housing, and adiffuser portion, wherein the gas generator housing is connected to oneend of the pressurized gas chamber housing and the diffuser portion isconnected to the other end of the pressurized gas housing, and a firstrupturable plate closes between the pressurized gas chamber and the gasgenerator and a second rupturable plate closes between the pressurizedgas chamber and the diffuser portion.
 64. An inflator according to claim63, wherein a cap having a gas ejecting hole provided in at least one ofa side surface and an end surface thereof covers the first repturableplate from the pressurized gas chamber side.
 65. An inflator accordingto claims 63 or 64, wherein the gas generator housing and thepressurized gas chamber housing, and the diffuser portion and thepressurized gas chamber housing are connected by resistance-welding. 66.An inflator according to claim 63 or 64, wherein the outer diameters ofthe pressurized gas chamber housing, the gas generator housing and thediffuser portion are equal or approximate to one another.
 67. Aninflator inflating an airbag with pressurized gas, wherein thepressurized gas is charged in a pressurized gas chamber having an outershell formed by a cylindrical pressurized gas chamber housing, thepressurized gas chamber housing is symmetrical regarding the axial andradial directions and both ends thereof are reduced in diameter.
 68. Aninflator according to claim 67, using combustion gas obtained bycombustion of a gas generating agent together with pressurized gas as ainflating means for an air bag, and comprising a pressurized gas chamberhaving an outer shell formed by a cylindrical pressurized gas chamberhousing and charged with pressurized gas, a gas generator for generatingcombustion gas, and a diffuser portion having a gas discharging hole,wherein the pressurized gas chamber housing is symmetrical regarding theaxial and radial directions and both ends thereof are reduced indiameter.
 69. An inflator according to claim 68, wherein the gasgenerator has an outer shell formed by a gas generator housing andincluding an ignition means and a gas generating agent inside thehousing, the gas generator housing is connected to one end of thepressurized gas chamber housing and the diffuser portion is connected tothe other end of the pressurized gas housing, and a first rupturableplate closes between the pressurized gas chamber and the gas generatorand a second rupturable plate closes between the pressurized gas chamberand the diffuser portion.
 70. An inflator according to claim 68, whereinone or both of a set of the gas generator housing and the pressurizedgas chamber housing, and a set of the diffuser portion and thepressurized gas chamber housing are connected by resistance-welding. 71.An inflator according to claim 67, substantially using only pressurizedgas as an inflating means for an air bag, and comprising a pressurizedgas chamber having an outer shell formed by a cylindrical pressurizedgas chamber housing and charged with pressurized gas, and a diffuserportion connected to the pressurized gas chamber and having a gasdischarging hole, wherein a rupturable plate closes between thepressurized gas chamber and the diffuser portion and an igniter which isa rupturing means for the rupturable plate is accommodated in thediffuser portion, and the pressurized gas chamber housing is symmetricalregarding the axial and radial directions and both ends thereof arereduced in diameter.
 72. An inflator according to claim 71, wherein acylindrical gas discharging port connected to the gas discharging holeof the diffuser portion is provided, the gas discharging port is mountedto coincide with the axial direction of the pressurized gas chamberhousing, and the pressurized gas discharged from the gas discharginghole passes through the gas discharging port and is discharged from anopening provided in the gas discharging port to inflate the air bag. 73.An inflator according to claim 71, wherein the diffuser portion and thepressurized gas chamber housing are connected to each other byresistance-welding.
 74. An air bag system provided with anactuation-signal outputting means comprising an impact sensor and acontrol unit, and a module case accommodating an inflator according toclaim 52 and an air bag.